Anthracene compound, light-emitting element, light-emitting device, electronic appliance, and lighting device

ABSTRACT

An organic compound having a high T 1  level is provided. An element emitting phosphorescence in the blue and green regions is provided. An organic compound having a high glass-transition temperature is provided. A light-emitting element, a light-emitting device, an electronic appliance, or a lighting device having high heat resistance is provided. A light-emitting element includes at least a hole-transport layer, a light-emitting layer, and an electron-transport layer between an anode and a cathode. An anthracene compound represented by General Formula (G1) is contained in at least one of the hole-transport layer, the light-emitting layer, and the electron-transport layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an anthracene compound and alight-emitting element containing the anthracene compound as alight-emitting substance. The present invention also relates to alight-emitting device, an electronic appliance, and a lighting deviceeach of which includes the light-emitting element.

2. Description of the Related Art

In recent years, research and development have been extensivelyconducted on light-emitting elements utilizing electroluminescence (EL)(Patent Document 1 and Patent Document 2). In a basic structure of sucha light-emitting element, a layer containing a light-emitting substance(a light-emitting layer) is provided between a pair of electrodes. Byapplying voltage to the element, light emission from the light-emittingsubstance can be obtained.

Such a light-emitting element is a self-luminous element; thus, adisplay (a display device) including the light-emitting element hasadvantages over a liquid crystal display in point of high visibility, nobacklight required, and the like. Besides, such a light-emitting elementhas advantages in that it can be manufactured to be thin and lightweightand has very fast response speed.

Since a light-emitting layer of such a light-emitting element can beformed in the form of a film, planar light emission can be achieved.This feature is difficult to obtain with point light sources typified byincandescent lamps and LEDs or linear light sources typified byfluorescent lamps. Thus, the light-emitting element also has greatpotential as a planar light source applicable to a lighting device andthe like.

In the case of an organic EL element in which a light-emitting layercontaining an organic compound as a light-emitting substance is providedbetween a pair of electrodes, application of voltage between the pair ofelectrodes causes injection of electrons from a cathode and holes froman anode into the light-emitting layer, so that a current flows. Byrecombination of the injected electrons and holes, the light-emittingorganic compound is brought into an excited state to provide lightemission.

An organic EL element is known in which an electron-injection layer, ahole-injection layer, an electron-transport layer, and a hole-transportlayer are provided between a cathode and an anode for efficientinjection of electrons and holes to a light-emitting layer. In such anorganic EL element, an anode, a hole-injection layer, a hole-transportlayer, a light-emitting layer, an electron-transport layer, anelectron-injection layer, and a cathode are generally stacked in thisorder.

It is known that a small amount of dopant material with high emissionefficiency is dispersed in a host material in a light-emitting layer, sothat the emission efficiency can be improved. In the light-emittinglayer having such a structure, electrons and holes are recombined firstin the host material, so that the host material is brought into anexcited state. Then the excited energy is transferred to the dopantmaterials to excite the dopant materials, so that light emission fromthe dopant materials can be obtained. Such an energy transfer mechanismcan improve the emission efficiency of a light-emitting element.

The excited state of an organic compound can be a singlet excited stateor a triplet excited state, and light emission from the singlet excitedstate (S₁) is referred to as fluorescence, and light emission from thetriplet excited state (T₁) is referred to as phosphorescence. Thestatistical generation ratio of the excited states in the light-emittingelement is considered to be S₁:T₁=1:3. Therefore, a light-emittingelement including a phosphorescent compound capable of converting thetriplet excited state into light emission has been actively developed inrecent years.

An element that emits light in the blue and green regions is mostdemanded of light-emitting elements containing phosphorescent compounds.

REFERENCES Patent Documents

-   Patent Document 1: U.S. Pat. No. 6,984,462-   Patent Document 2: Chinese Patent Application Publication No.    1338499

SUMMARY OF THE INVENTION

In a phosphorescent element, a compound having a triplet excited state(T₁) energy level higher than that of a phosphorescent dopant materialneeds to be used as a host material for a light-emitting layer.Therefore, a host material used in a light-emitting element emittinglight in the blue and green regions needs to have a higher T₁ level thana host material used in a light-emitting element emitting light having alonger wavelength than light in the blue and green regions.

It is preferable that a light-emitting element have high heat resistancefor a longer lifetime. A compound with a high glass-transitiontemperature (Tg) may be used in order to improve the heat resistance ofa light-emitting element.

An object of one embodiment of the present invention is to provide ananthracene compound with a high T₁ level. Another object is to provide alight-emitting element that emits phosphorescence in the blue and greenregions. Another object is to provide an anthracene compound with a highglass-transition temperature. Another object is to provide alight-emitting element, a light-emitting device, an electronicappliance, or a lighting device with high heat resistance.

One embodiment of the present invention is a light-emitting element thatincludes at least a hole-transport layer, a light-emitting layer, and anelectron-transport layer between an anode and a cathode. Thelight-emitting layer contains an anthracene compound represented byGeneral Formula (G1) and a phosphorescent compound. At least one of thehole-transport layer and the electron-transport layer contains theanthracene compound represented by General Formula (G1).

In the formula, α represents a substituted or unsubstituted m-phenylenegroup or a substituted or unsubstituted 3,3′-biphenyldiyl group; and Arrepresents any of a substituted or unsubstituted phenyl group, asubstituted or unsubstituted biphenyl group, a substituted orunsubstituted carbazolyl group, a substituted or unsubstituteddibenzothiophenyl group, a substituted or unsubstituted dibenzofuranylgroup, a substituted or unsubstituted triphenylenyl group, a substitutedor unsubstituted naphthyl group, a substituted or unsubstitutedphenanthrenyl group, a substituted or unsubstituted fluorenyl group, asubstituted or unsubstituted pyridyl group, a substituted orunsubstituted pyrimidyl group, a substituted or unsubstituteddibenzoquinoxalinyl group, a substituted or unsubstituted benzimidazolylgroup, and a substituted or unsubstituted benzoxazolyl group. In thecase where a substituent is bonded to Ar, the substituent is any of aphenyl group, a biphenyl group, and an alkyl group having 1 to 6 carbonatoms.

Another embodiment of the present invention is a light-emitting elementthat includes at least a hole-transport layer, a light-emitting layer,and an electron-transport layer between an anode and a cathode. Theelectron-transport layer contains the anthracene compound represented byGeneral Formula (G1) and an electron-transport organic compound.

Another embodiment of the present invention is a light-emitting elementthat includes at least a hole-transport layer, a light-emitting layer,and an electron-transport layer between an anode and a cathode. Thehole-transport layer contains the anthracene compound represented byGeneral Formula (G1) and a hole-transport organic compound.

Another embodiment of the present invention is a light-emitting elementthat includes at least a hole-transport layer, a light-emitting layer,and an electron-transport layer between an anode and a cathode. Thelight-emitting layer contains the anthracene compound represented byGeneral Formula (G1) and a phosphorescent compound. The hole-transportlayer contains the anthracene compound represented by General Formula(G1) and a hole-transport organic compound. The electron-transport layercontains the anthracene compound represented by General Formula (G1) andan electron-transport organic compound.

Another embodiment of the present invention is a light-emitting elementthat includes at least a hole-transport layer, a light-emitting layer,and an electron-transport layer between an anode and a cathode. Thelight-emitting layer contains an electron-transport compound or ahole-transport compound, the anthracene compound represented by GeneralFormula (G1), and a phosphorescent compound. The hole-transport layercontains the anthracene compound represented by General Formula (G1) anda hole-transport organic compound. The electron-transport layer containsthe anthracene compound represented by General Formula (G1) and anelectron-transport organic compound.

In the above-described structure, a peak on the shortest wavelength sideof phosphorescence can be 570 nm or less.

Another embodiment of the present invention is a compound represented byStructural Formula (100).

Another embodiment of the present invention is a compound represented byStructural Formula (103).

Another embodiment of the present invention is a compound represented byStructural Formula (112).

According to one embodiment of the present invention, a compound with ahigh T₁ level can be provided. In addition, a light-emitting elementthat emits phosphorescence in the blue and green regions can beprovided. In addition, a compound with a high glass-transitiontemperature (Tg) can be provided. In addition, a light-emitting element,a light-emitting device, an electronic appliance, or a lighting devicewith high heat resistance can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a light-emitting element of oneembodiment of the present invention.

FIGS. 2A to 2D each illustrate an example of a light-emitting element ofone embodiment of the present invention.

FIG. 3 illustrates an example of a light-emitting element of oneembodiment of the present invention.

FIGS. 4A and 4B each illustrate an example of a light-emitting elementof one embodiment of the present invention.

FIGS. 5A to 5E illustrate examples of electronic appliances.

FIGS. 6A and 6B illustrate examples of lighting devices.

FIG. 7 illustrates a light-emitting element of Examples.

FIGS. 8A and 8B are ¹H NMR charts of an anthracene compound (2mTPDfha)represented by Structural Formula (100).

FIGS. 9A and 9B show results of LC/MS analysis of the anthracenecompound (2mTPDfha) represented by Structural Formula (100).

FIGS. 10A and 10B are ¹H NMR charts of an anthracene compound(2mCzPDfha) represented by Structural Formula (103).

FIG. 11 shows results of LC/MS analysis of the anthracene compound(2mCzPDfha) represented by Structural Formula (103).

FIG. 12 shows current density-luminance characteristics of alight-emitting element 1 manufactured in Example 4.

FIG. 13 shows voltage-luminance characteristics of the light-emittingelement 1 manufactured in Example 4.

FIG. 14 shows luminance-current efficiency characteristics of thelight-emitting element 1 manufactured in Example 4.

FIG. 15 shows voltage-current characteristics of the light-emittingelement 1 manufactured in Example 4.

FIG. 16 shows luminance-chromaticity characteristics of thelight-emitting element 1 manufactured in Example 4.

FIG. 17 shows current density-luminance characteristics of alight-emitting element 2 manufactured in Example 5.

FIG. 18 shows voltage-luminance characteristics of the light-emittingelement 2 manufactured in Example 5.

FIG. 19 shows voltage-current characteristics of the light-emittingelement 2 manufactured in Example 5.

FIG. 20 shows luminance-chromaticity characteristics of thelight-emitting element 2 manufactured in Example 5.

FIG. 21 shows an emission spectrum of the light-emitting element 2manufactured in Example 5.

FIG. 22 shows current density-luminance characteristics of alight-emitting element 3 manufactured in Example 6.

FIG. 23 shows voltage-luminance characteristics of the light-emittingelement 3 manufactured in Example 6.

FIG. 24 shows luminance-current efficiency characteristics of thelight-emitting element 3 manufactured in Example 6.

FIG. 25 shows voltage-current characteristics of the light-emittingelement 3 manufactured in Example 6.

FIG. 26 shows luminance-chromaticity characteristics of thelight-emitting element 3 manufactured in Example 6.

FIG. 27 shows an emission spectrum of the light-emitting element 3manufactured in Example 6.

FIGS. 28A and 28B show calculation results in Example 8.

FIG. 29 shows luminance-current efficiency characteristics of acomparative light-emitting element 1 and a comparative light-emittingelement 2 manufactured in Example 8.

FIG. 30 shows voltage-current characteristics of the comparativelight-emitting element 1 and the comparative light-emitting element 2manufactured in Example 8.

FIG. 31 shows luminance-chromaticity characteristics of the comparativelight-emitting elements 1 and 2 manufactured in Example 8.

FIG. 32 shows emission spectra of the comparative light-emittingelements 1 and 2 manufactured in Example 8.

FIG. 33 shows voltage-current characteristics of a comparativelight-emitting element 3 manufactured in Example 8.

FIG. 34 shows luminance-chromaticity characteristics of the comparativelight-emitting element 3 manufactured in Example 8.

FIG. 35 shows an emission spectrum of the comparative light-emittingelement 3 manufactured in Example 8.

FIG. 36 shows voltage-current characteristics of the light-emittingelement 2 manufactured in Example 5 and the comparative light-emittingelement 3 manufactured in Example 8.

FIGS. 37A and 37B show results of LC/MS analysis of an anthracenecompound (2mDBqPDfha) represented by Structural Formula (112).

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments and examples of the present invention will bedescribed in detail with reference to the accompanying drawings. Notethat the present invention is not limited to the following description,and various changes and modifications can be made without departing fromthe spirit and scope of the present invention. Therefore, the presentinvention should not be construed as being limited to the description inthe following embodiments and examples.

Embodiment 1

In this embodiment, light-emitting elements each of which is oneembodiment of the present invention are described with reference to FIG.1, FIGS. 2A to 2D, and FIG. 3.

As illustrated in FIG. 1, the light-emitting element of one embodimentof the present invention includes an anode 101, a hole-transport layer103 over the anode 101, a light-emitting layer 104 on and in contactwith the hole-transport layer 103, an electron-transport layer 105 onand in contact with the light-emitting layer 104, and a cathode 102 overthe electron-transport layer 105. When voltage higher than the thresholdvoltage of the light-emitting element is applied between the anode 101and the cathode 102, holes are injected from the anode 101 side andelectrons are injected from the cathode 102 side to an EL layer 106including at least the hole-transport layer 103, the light-emittinglayer 104, and the electron-transport layer 105. The injected electronsand holes are recombined in the EL layer 106 and a light-emittingsubstance contained in the EL layer 106 emits light.

The light-emitting element of one embodiment of the present invention isa light-emitting element that includes at least the hole-transport layer103, the light-emitting layer 104, and the electron-transport layer 105between the anode 101 and the cathode 102. In the light-emittingelement, an anthracene compound represented by General Formula (G1) iscontained in at least one of the light-emitting layer 104, thehole-transport layer 103, and the electron-transport layer 105.

In the formula, α represents a m-phenylene group or a 3,3′-biphenyldiylgroup; and Ar represents any of a substituted or unsubstituted phenylgroup, a substituted or unsubstituted biphenyl group, a substituted orunsubstituted carbazolyl group, a substituted or unsubstituteddibenzothiophenyl group, a substituted or unsubstituted dibenzofuranylgroup, a substituted or unsubstituted triphenylenyl group, a substitutedor unsubstituted naphthyl group, a substituted or unsubstitutedphenanthrenyl group, a substituted or unsubstituted fluorenyl group, asubstituted or unsubstituted pyridyl group, a substituted orunsubstituted pyrimidyl group, a substituted or unsubstituteddibenzoquinoxalinyl group, a substituted or unsubstituted benzimidazolylgroup, and a substituted or unsubstituted benzoxazolyl group.

In the case where a substituent is bonded to Ar, the substituent is aphenyl group, a biphenyl group, or an alkyl group having 1 to 6 carbonatoms. Such a substituent is preferably used, in which case thestructure becomes sterical; thus, a film including such a substituent isnot easily crystallized and uniform film quality is easily obtained. Anaryl group is preferably used as the substituent, in which case heatresistance is improved. The biphenyl group is more preferably ameta-biphenyl group or an ortho-biphenyl group than a para-biphenylgroup, in which case the T₁ level is not easily reduced. The alkyl groupis preferably used as the substituent, in which case solubility in anorganic solvent is increased. The alkyl group is preferably used as thesubstituent, in which case the T₁ level is not easily reduced. It ispreferable that such a substituent be not used, in which case the T₁level is not easily reduced and can be kept high.

In the case where the anthracene compound represented by General Formula(G1) is used as a host material for a blue phosphorescent dopantmaterial, a substituted or unsubstituted phenyl group, a substituted orunsubstituted biphenyl group, a substituted or unsubstituted carbazolylgroup, a substituted or unsubstituted dibenzothiophenyl group, asubstituted or unsubstituted dibenzofuranyl group, a substituted orunsubstituted fluorenyl group, a substituted or unsubstituted pyridylgroup, a substituted or unsubstituted pyrimidyl group, a substituted orunsubstituted benzimidazolyl group, and a substituted or unsubstitutedbenzoxazolyl group are particularly preferable because of their higherT₁ levels. Furthermore, a substituted or unsubstituted phenyl group, asubstituted or unsubstituted biphenyl group, and a substituted orunsubstituted carbazol-9-yl group are more preferable because of theirhigh T₁ levels.

A compound with a high molecular weight generally has a highglass-transition temperature (Tg). However, such a compound with a highmolecular weight has conjugation that extends easily and an S₁ and T₁levels that are reduced easily. Meanwhile, the anthracene compoundrepresented by General Formula (G1) has a high molecular weight and highTg but has a high S₁ and T₁ levels. The reason for the high Tg isprobably as follows: planes of two fluorene skeletons are orthogonallybonded to the 9-position and the 9′-position of an anthracene skeletonat approximately 90°, which provides high three dimensionality. For thisreason, the anthracene compound is preferably mixed with a material thatis crystallized easily, in which case film quality is improved. Thereason for the high S₁ and T₁ levels is thought to be as follows: the9-position and the 9′-position of the anthracene skeleton each have acarbon-carbon sigma bond, which suppresses extension of the conjugationbetween the anthracene skeleton and the fluorene skeleton bondedthereto. In addition, another reason is thought to be as follows: thissigma bond prevents conjugation from a substituent (α-Ar) bonded to the2-position of the anthracene skeleton from extending beyond a benzeneskeleton including the 2-position of the anthracene skeleton. The S₁ andT₁ levels are high for the above-described reason, and a gap between thehighest occupied molecular orbital (HOMO) level and the lowestunoccupied molecular orbital (LUMO) level is large. Thus, the anthracenecompound is preferably contained in a carrier-transport layer, in whichcase a carrier-blocking property and an exciton-blocking property areimproved. Owing to the high S₁ and T₁ levels, the anthracene compoundcan be suitably used for a light-emitting layer in a light-emittingelement emitting light with a short wavelength such as light in the blueor green region.

Since Ar is bonded to the anthracene skeleton via m-phenylenerepresented by α in the anthracene compound represented by GeneralFormula (G1), extension of the conjugation can be suppressed more thanin the case where Ar is bonded to the anthracene skeleton viap-phenylene. Thus, the anthracene compound has a high T₁ level.

For this reason, the anthracene compound represented by General Formula(G1) can be suitably used as a host material for the light-emittinglayer 104 in a light-emitting element emitting light with shortwavelengths in the visible range such as phosphorescence in the blue andgreen regions. In addition, the anthracene compound represented byGeneral Formula (G1) is contained in at least one of the light-emittinglayer 104, the hole-transport layer 103, and the electron-transportlayer 105, so that a light-emitting element with high heat resistancecan be obtained.

The anthracene compound represented by General Formula (G1) can also besuitably mixed with other compounds contained in the light-emittinglayer 104, the hole-transport layer 103, and the electron-transportlayer 105.

For example, as illustrated in FIG. 2A, the hole-transport layer 103 maycontain an anthracene compound 201 represented by General Formula (G1)and a hole-transport compound 203. In this case, Ar in General Formula(G1) representing the anthracene compound is preferably any of asubstituted or unsubstituted biphenyl group, a substituted orunsubstituted carbazolyl group, a substituted or unsubstituteddibenzothiophenyl group, a substituted or unsubstituted dibenzofuranylgroup, a substituted or unsubstituted triphenylenyl group, a substitutedor unsubstituted naphthyl group, a substituted or unsubstitutedphenanthrenyl group, and a substituted or unsubstituted fluorenyl group,in which case the hole-transport property is high.

As illustrated in FIG. 2B, the electron-transport layer 105 may containthe anthracene compound 201 represented by General Formula (G1) and anelectron-transport compound 205. In this case, Ar in General Formula(G1) representing the anthracene compound is preferably any of asubstituted or unsubstituted pyridyl group, a substituted orunsubstituted pyrimidyl group, a substituted or unsubstituteddibenzoquinoxalinyl group, a substituted or unsubstituted benzimidazolylgroup, and a substituted or unsubstituted benzoxazolyl group.

As illustrated in FIG. 2C, the light-emitting layer 104 may contain theanthracene compound 201 represented by General Formula (G1) and aphosphorescent compound 204 a, the hole-transport layer 103 may containthe anthracene compound 201 represented by General Formula (G1) and thehole-transport compound 203, and the electron-transport layer 105 maycontain the anthracene compound 201 represented by General Formula (G1)and the electron-transport compound 205.

As illustrated in FIG. 2D, the light-emitting layer 104 may contain theanthracene compound 201 represented by General Formula (G1), thephosphorescent compound 204 a, and an electron-transport orhole-transport compound 204 b, the hole-transport layer 103 may containthe anthracene compound 201 represented by General Formula (G1) and thehole-transport compound 203, and the electron-transport layer 105 maycontain the anthracene compound 201 represented by General Formula (G1)and the electron-transport compound 205.

As illustrated in FIG. 3, a hole-injection layer 107 may be providedbetween the anode 101 and the hole-transport layer 103. In addition, anelectron-injection layer 108 may be provided between the cathode 102 andthe electron-transport layer 105. In addition, a charge-generation layer109 may be provided between the cathode 102 and the electron-injectionlayer 108.

The hole-injection layer 107 contains a substance having a highhole-transport property and an acceptor substance. When electrons areextracted from the substance having a high hole-transport property owingto the acceptor substance, holes are generated. Thus, holes are injectedfrom the hole-injection layer 107 into the light-emitting layer 104through the hole-transport layer 103. The anthracene compoundrepresented by General Formula (G1) may be used as the substance havinga high hole-transport property. In this case, Ar in General Formula (G1)representing the anthracene compound is preferably any of a substitutedor unsubstituted biphenyl group, a substituted or unsubstitutedcarbazolyl group, a substituted or unsubstituted dibenzothiophenylgroup, a substituted or unsubstituted dibenzofuranyl group, asubstituted or unsubstituted triphenylenyl group, a substituted orunsubstituted naphthyl group, a substituted or unsubstitutedphenanthrenyl group, and a substituted or unsubstituted fluorenyl group,in which case the hole-transport property is high.

The charge-generation layer 109 contains a substance having a highhole-transport property and an acceptor substance. Electrons areextracted from the substance having a high hole-transport property owingto the acceptor substance, and the extracted electrons are injected fromthe electron-injection layer 108 having an electron-injection propertyinto the light-emitting layer 104 through the electron-transport layer105.

Specific examples of the anthracene compound represented by GeneralFormula (G1) include anthracene compounds represented by StructuralFormulae 100 to 112. However, the present invention is not limitedthereto.

An example of a method for synthesizing the anthracene compoundrepresented by General Formula (G1) is described below. Note that themethod for synthesizing the anthracene compound represented by GeneralFormula (G1) is not limited to the method described below.

<<Method for Synthesizing Anthracene Compound Represented by GeneralFormula (G1)>>

In the formula, α represents a m-phenylene group or a 3,3′-biphenyldiylgroup; and Ar represents any of a substituted or unsubstituted phenylgroup, a substituted or unsubstituted biphenyl group, a substituted orunsubstituted carbazolyl group, a substituted or unsubstituteddibenzothiophenyl group, a substituted or unsubstituted dibenzofuranylgroup, a substituted or unsubstituted triphenylenyl group, a substitutedor unsubstituted naphthyl group, a substituted or unsubstitutedphenanthrenyl group, a substituted or unsubstituted fluorenyl group, asubstituted or unsubstituted pyridyl group, a substituted orunsubstituted pyrimidyl group, a substituted or unsubstituteddibenzoquinoxalinyl group, a substituted or unsubstituted benzimidazolylgroup, and a substituted or unsubstituted benzoxazolyl group. In thecase where a substituent is bonded to Ar, the substituent is a phenylgroup, a biphenyl group, or an alkyl group having 1 to 6 carbon atoms.

Synthesis Scheme (g) of the anthracene compound represented by GeneralFormula (G1) is shown below.

In Synthesis Scheme (g), α represents a m-phenylene group or a3,3′-biphenyldiyl group; and Ar represents any of a substituted orunsubstituted phenyl group, a substituted or unsubstituted biphenylgroup, a substituted or unsubstituted carbazolyl group, a substituted orunsubstituted dibenzothiophenyl group, a substituted or unsubstituteddibenzofuranyl group, a substituted or unsubstituted triphenylenylgroup, a substituted or unsubstituted naphthyl group, a substituted orunsubstituted phenanthrenyl group, a substituted or unsubstitutedfluorenyl group, a substituted or unsubstituted pyridyl group, asubstituted or unsubstituted pyrimidyl group, a substituted orunsubstituted dibenzoquinoxalinyl group, a substituted or unsubstitutedbenzimidazolyl group, and a substituted or unsubstituted benzoxazolylgroup. In the case where a substituent is bonded to Ar, the substituentis a phenyl group, a biphenyl group, or an alkyl group having 1 to 6carbon atoms. In addition, X represents halogen; bromine or iodine ispreferable because of its high reactivity. In addition, R represents analkyl group or hydrogen.

As shown in Synthesis Scheme (g), an anthracene halide (Compound (p1))is coupled with an aryl boron compound or aryl boronic acid (Compound(p2)) by the Suzuki-Miyaura coupling, so that the anthracene compoundrepresented by General Formula (G1) can be obtained.

Examples of palladium catalysts that can be used in Synthesis Scheme (g)include, but are not limited to, palladium(II) acetate,tetrakis(triphenylphosphine)palladium(0), andbis(triphenylphosphine)palladium(II) dichloride.

Examples of ligands of the palladium catalyst that can be used inSynthesis Scheme (g) include, but are not limited to,tri(ortho-tolyl)phosphine, triphenylphosphine, andtricyclohexylphosphine.

Examples of bases that can be used in Synthesis Scheme (g) include, butare not limited to, an organic base such as sodium tert-butoxide and aninorganic base such as potassium carbonate or sodium carbonate.

Examples of a solvent that can be used in the synthesis scheme (g)include, but not limited to, a mixed solvent of toluene and water; amixed solvent of toluene, alcohol such as ethanol, and water; a mixedsolvent of xylene and water; a mixed solvent of xylene, alcohol such asethanol, and water; a mixed solvent of benzene and water; a mixedsolvent of benzene, alcohol such as ethanol, and water; and a mixedsolvent of water and an ether such as ethylene glycol dimethyl ether.Note that a mixed solvent of toluene and water; a mixed solvent oftoluene, ethanol, and water; or a mixed solvent of water and ether suchas ethylene glycol dimethyl ether is more preferable.

As the coupling reaction in Synthesis Scheme (g), the Suzuki-Miyauracoupling using the organoboron compound or the boronic acid representedby Compound (p2) may be replaced with a cross coupling reaction using anorganoaluminum compound, an organozirconium compound, an organozinccompound, an organotin compound, or the like. However, the presentinvention is not limited thereto.

In Synthesis Scheme (g), a boron compound of anthracene or a boronicacid compound of anthracene may be coupled with a halogenated arylcompound or aryl triflate by the Suzuki-Miyaura coupling.

In the above-described manner, the anthracene compound represented byGeneral Formula (G1) can be synthesized.

A specific example in which the light-emitting element described in thisembodiment is manufactured is described below.

For the anode 101 and the cathode 102, any of metals, alloys,electrically conductive compounds, and mixtures thereof, and the likecan be used. Specifically, indium oxide-tin oxide (indium tin oxide),indium oxide-tin oxide containing silicon or silicon oxide, indiumoxide-zinc oxide (indium zinc oxide), indium oxide containing tungstenoxide and zinc oxide, gold (Au), platinum (Pt), nickel (Ni), tungsten(W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper(Cu), palladium (Pd), and titanium (Ti) can be used. In addition, anelement belonging to Group 1 or Group 2 of the periodic table, forexample, an alkali metal such as lithium (Li) or cesium (Cs), analkaline earth metal such as calcium (Ca) or strontium (Sr), ormagnesium (Mg), an alloy containing such an element (MgAg, AlLi), a rareearth metal such as europium (Eu) or ytterbium (Yb), an alloy containingsuch an element, graphene, and the like can be used. Note that the anode101 and the cathode 102 can be formed by, for example, a sputteringmethod or an evaporation method (including a vacuum evaporation method).

Examples of the substance having a high hole-transport property that isused for the hole-injection layer 107, the hole-transport layer 103, andthe charge-generation layer 109 include aromatic amine compounds such as4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB orα-NPD),N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: TPD), 4,4′,4″-tris(carbazol-9-yl)triphenylamine(abbreviation: TCTA), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine(abbreviation: TDATA),4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: MTDATA), and4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB);3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1);3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2); and3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1). A carbazole compound, such as4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP),1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), or9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA),or the like can also be used. These materials given here are mainlysubstances having a hole mobility of 10⁻⁶ cm²/Vs or higher. Note thatany other substances may also be used as long as the substances havehole-transport properties higher than electron-transport properties.

Further, a high molecular compound such as poly(N-vinylcarbazole)(abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA),poly[N-(4-{N′-[4-(4-diphenylamino)phenyl]phenyl-N′-phenylamino}phenyl)methacrylamide](abbreviation: PTPDMA), orpoly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine] (abbreviation:Poly-TPD) can be used.

Note that the anthracene compound represented by General Formula (G1)can also be used as the substance having a high hole-transport property.

Examples of the acceptor substance that is used for the hole-injectionlayer 107 and the charge-generation layer 109 include a transition metaloxide and an oxide of a metal belonging to any of Groups 4 to 8 of theperiodic table. Specifically, molybdenum oxide is particularlypreferable.

The light-emitting layer 104 contains a light-emitting substance. Thelight-emitting layer 104 may contain only a light-emitting substance;alternatively, an emission center substance may be dispersed in a hostmaterial in the light-emitting layer 104. Alternatively, a mixture oftwo or more kinds of host materials may be used.

There is no particular limitation on the material that can be used asthe light-emitting substance and the emission center substance in thelight-emitting layer 104, and light emitted from the substance may beeither fluorescence or phosphorescence. Given below are examples of thelight-emitting substance and the emission center substance.

As the substance emitting fluorescence, known materials can be used. Theanthracene compound represented by General Formula (G1) may also beused.

Examples of the substance that emits phosphorescence includebis[2-(3′,5′-bistrifluoromethylphenyl)pyridinato-N,C^(2′)]iridium(III)picolinate(abbreviation: [Ir(CF₃ppy)₂(pic)]),bis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III)acetylacetonate(abbreviation: FIracac), tris(2-phenylpyridinato)iridium(III)(abbreviation: [Ir(ppy)₃]),bis(2-phenylpyridinato)iridium(III)acetylacetonate (abbreviation:[Ir(ppy)₂(acac)]), tris(acetylacetonato)(monophenanthroline)terbium(III)(abbreviation: Tb(acac)₃(Phen)),bis(benzo[h]quinolinato)iridium(III)acetylacetonate (abbreviation:[Ir(bzq)₂(acac)]),bis(2,4-diphenyl-1,3-oxazolato-N,C^(2′))iridium(III)acetylacetonate(abbreviation: [Ir(dpo)₂(acac)]),bis[2-(4′-perfluorophenylphenyl)pyridinato]iridium(III)acetylacetonate(abbreviation: [Ir(p-PF-ph)₂(acac)]),bis(2-phenylbenzothiazolato-N,C^(2′))iridium(III)acetylacetonate(abbreviation: [Ir(bt)₂(acac)]),bis[2-(2′-benzo[4,5-α]thienyl)pyridinato-N,C^(2′)]iridium(III)acetylacetonate(abbreviation: [Ir(btp)₂(acac)]),bis(1-phenylisoquinolinato-N,C^(2′))iridium(III)acetylacetonate(abbreviation: [Ir(piq)₂(acac)]),(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)(abbreviation: [Ir(Fdpq)₂(acac)]),(acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III)(abbreviation: [Ir(tppr)₂(acac)]),2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II)(abbreviation: PtOEP),tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III)(abbreviation: [Eu(DBM)₃(Phen)]), andtris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III)(abbreviation: [Eu(TTA)₃(Phen)]).

There is no particular limitation on the material that can be used asthe above-described host material. Examples of the material includeexample: metal complexes such as tris(8-quinolinolato)aluminum(III)(abbreviation: Alq), tris(4-methyl-8-quinolinolato)aluminum(III)(abbreviation: Almq₃), bis(10-hydroxybenzo[h]quinolinato)beryllium(II)(abbreviation: BeBq₂),bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III)(abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq),bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), andbis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ);heterocyclic compounds such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: TAZ),2,2′,2″-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole)(abbreviation: TPBI), bathophenanthroline (abbreviation: BPhen),bathocuproine (abbreviation: BCP), and9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation:CO11); and aromatic amine compounds such as4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB orα-NPD),N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: TPD), and4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB). In addition, condensed polycyclic aromaticcompounds such as anthracene derivatives, phenanthrene derivatives,pyrene derivatives, chrysene derivatives, and dibenzo[g,p]chrysenederivatives can be given, and specific examples are9,10-diphenylanthracene (abbreviation: DPAnth),N,N-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: CzAlPA), 4-(10-phenyl-9-anthryl)triphenylamine(abbreviation: DPhPA),4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine(abbreviation: YGAPA),N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: PCAPA),N,9-diphenyl-N-{4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carbazol-3-amine(abbreviation: PCAPBA),N,9-diphenyl-N-(9,10-diphenyl-2-anthryl)-9H-carbazol-3-amine(abbreviation: 2PCAPA), 6,12-dimethoxy-5,11-diphenylchrysene,N,N,N′,N′,N″,N″,N′″,N′″-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetramine(abbreviation: DBC1), 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole(abbreviation: CzPA),3,6-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole(abbreviation: DPCzPA), 9,10-bis(3,5-diphenylphenyl)anthracene(abbreviation: DPPA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA),2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA),9,9′-bianthryl (abbreviation: BANT),9,9′-(stilbene-3,3′-diyl)diphenanthrene (abbreviation: DPNS),9,9′-(stilbene-4,4′-diyl)diphenanthrene (abbreviation: DPNS2), and3,3′,3″-(benzene-1,3,5-triyl)tripyrene (abbreviation: TPB3). One or moresubstances having a wider energy gap than the above-described emissioncenter substance described above is preferably selected from thesesubstances and known substances. Moreover, in the case where theemission center substance emits phosphorescence, a substance havinghigher triplet excitation energy (an energy difference between a groundstate and a triplet excited state) than the emission center substancemay be selected as the host material.

As the material that can be used as the host material, the anthracenecompound represented by General Formula (G1) can also be used. Theanthracene compound represented by General Formula (G1) has a high T₁level. Thus, by using the anthracene compound as the host material for aphosphorescent substance, a light-emitting element emitting light in theblue and green regions can be achieved.

Note that the light-emitting layer 104 may have a structure in which twoor more layers are stacked. For example, in the case where thelight-emitting layer 104 is formed by stacking a first light-emittinglayer and a second light-emitting layer in that order over thehole-transport layer, a substance having a hole-transport property isused as the host material for the first light-emitting layer and asubstance having an electron-transport property is used as the hostmaterial for the second light-emitting layer.

The electron-transport layer 105 contains a substance having a highelectron-transport property. For the electron-transport layer 105, ametal complex such as Alq₃, tris(4-methyl-8-quinolinolato)aluminum(III)(abbreviation: Almq₃), bis(10-hydroxybenzo[h]quinolinato)beryllium(II)(abbreviation: BeBq₂), BAlq, Zn(BOX)₂, orbis[2-(2-hydroxyphenyl)benzothiazolato]zinc(II) (abbreviation: Zn(BTZ)₂)can be used. A heteroaromatic compound such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: TAZ),3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: BPhen),bathocuproine (abbreviation: BCP), or4,4′-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs) can alsobe used. A high molecular compound such as poly(2,5-pyridinediyl)(abbreviation: PPy),poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)](abbreviation: PF-Py) orpoly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2′-bipyridine-6,6′-diyl)](abbreviation: PF-BPy) can also be used. The substances given here aremainly substances having an electron mobility of 10⁻⁶ cm²/Vs or higher.Note that any other substances may also be used as long as thesubstances have electron-transport properties higher than hole-transportproperties.

Note that the anthracene compound represented by General Formula (G1)can also be used as the substance having a high electron-transportproperty.

The electron-transport layer is not limited to a single layer, and maybe a stack of two or more layers containing any of the above substances.

The electron-injection layer 108 contains a substance having a highelectron-injection property. For the electron-injection layer 108, analkali metal, an alkaline earth metal, or a compound thereof such aslithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF₂),or lithium oxide (LiO_(x)) can be used. A rare earth metal compound likeerbium fluoride (ErF₃) can also be used. Any of the above substances forforming the electron-transport layer 105 can also be used.

A composite material in which an organic compound and an electron donorare mixed may also be used for the electron-injection layer 108. Such acomposite material has an excellent electron-injection andelectron-transport properties because electrons are generated in theorganic compound by the electron donor. In this case, the organiccompound is preferably a material that is excellent in transporting thegenerated electrons. Specifically, for example, any of the abovesubstances for forming the electron-transport layer 105 (e.g., a metalcomplex or a heteroaromatic compound) can be used. As the electrondonor, a substance exhibiting an electron-donating property with respectto the organic compound may be used. Specifically, an alkali metal, analkaline earth metal, and a rare earth metal are preferable, andexamples thereof as lithium, cesium, magnesium, calcium, erbium, andytterbium. In addition, an alkali metal oxide or an alkaline earth metaloxide is preferable, and examples thereof are lithium oxide, calciumoxide, and barium oxide. A Lewis base such as magnesium oxide can alsobe used. An organic compound such as tetrathiafulvalene (abbreviation:TTF) can also be used.

Note that each of the above-described hole-injection layer 107,hole-transport layer 103, light-emitting layer 104, electron-transportlayer 105, electron-injection layer 108, and charge-generation layer 109can be formed by a method such as an evaporation method (e.g., a vacuumevaporation method), an ink-jet method, or a coating method.

In the above-described light-emitting element, current flows because ofa potential difference generated between the anode 101 and the cathode102 and holes and electrons are recombined in the EL layer 106, so thatlight can be emitted. Then, the emitted light is extracted outsidethrough one or both of the anode 101 and the cathode 102. Therefore, oneor both of the anode 101 and the cathode 102 are electrodes havinglight-transmitting properties.

In the above-described light-emitting element, the anthracene compoundrepresented by General Formula (G1) is contained in at least one of thehole-transport layer 103, the light-emitting layer 104, and theelectron-transport layer 105; thus, the above-described light-emittingelement can have high heat resistance.

Note that the light-emitting element described in this embodiment is anexample of a light-emitting element manufactured using the anthracenecompound that is one embodiment of the present invention. Further, as alight-emitting device including the above-described light-emittingelement, a passive matrix light-emitting device and an active matrixlight-emitting device can be manufactured. It is also possible tomanufacture a light-emitting device with a microcavity structureincluding a light-emitting element described in another embodiment,which is different from the above-described light-emitting elements.Each of the above-described light-emitting devices is included in thepresent invention. Note that the above-described light-emitting devicescan have improved heat resistance.

Note that there is no particular limitation on the structure of a TFT inthe case of manufacturing the active matrix light-emitting device. Forexample, a staggered TFT or an inverted staggered TFT can be used asappropriate. Further, a driver circuit formed over a TFT substrate maybe formed of both an n-type TFT and a p-type TFT or only either ann-type TFT or a p-type TFT. Furthermore, a semiconductor film used forthe TFT is not particularly limited. For example, a silicon film and anoxide semiconductor film can be used. In addition, the crystallinity ofthe semiconductor film is not particularly limited. For example, anamorphous semiconductor film and a semiconductor film with crystallinitycan be used.

Note that the anthracene compound that is one embodiment of the presentinvention can be used for an organic thin-film solar cell. Specifically,the anthracene compound can be used in a carrier-transport layer or acarrier-injection layer because the anthracene compound has acarrier-transport property. In addition, a film of a mixture of theanthracene compound and an acceptor substance can be used as acharge-generation layer. In addition, the anthracene compound can beused for a power-generation layer because the anthracene compound isphotoexcited.

Note that the structure described in this embodiment can be used asappropriate in combination with any of the structures described in theother embodiments.

Embodiment 2

In this embodiment, as one embodiment of the present invention, alight-emitting element (hereinafter referred to as tandem light-emittingelement) in which a charge-generation layer is provided between aplurality of EL layers is described with reference to FIGS. 4A and 4B.

As illustrated in FIG. 4A, the light-emitting element described in thisembodiment is a tandem light-emitting element including a plurality ofEL layers (a first EL layer 302(1) and a second EL layer 302(2)) betweena pair of electrodes (a first electrode 301 and a second electrode 304).

In this embodiment, the first electrode 301 functions as an anode, andthe second electrode 304 functions as a cathode. Note that the firstelectrode 301 and the second electrode 304 can have structures similarto those described in Embodiment 1. In addition, all or any of theplurality of EL layers (the first EL layer 302(1) and the second ELlayer 302(2)) may have structures similar to those described inEmbodiment 1. In other words, the structures of the first EL layer302(1) and the second EL layer 302(2) may be the same or different fromeach other and can be similar to those described in Embodiment 1.

Further, a charge-generation layer 305 is provided between the pluralityof EL layers (the first EL layer 302(1) and the second EL layer 302(2)).The charge-generation layer 305 has a function of injecting electronsinto one of the EL layers and injecting holes into the other of the ELlayers when a voltage is applied between the first electrode 301 and thesecond electrode 304. In this embodiment, when a voltage is applied suchthat the potential of the first electrode 301 is higher than that of thesecond electrode 304, the charge-generation layer 305 injects electronsinto the first EL layer 302(1) and injects holes into the second ELlayer 302(2).

Note that in terms of outcoupling efficiency, the charge-generationlayer 305 preferably has a property of transmitting visible light(specifically, the charge-generation layer 305 has a visible lighttransmittance of 40% or more). Further, the charge-generation layer 305functions even if it has lower conductivity than the first electrode 301or the second electrode 304.

The charge-generation layer 305 may have either a structure in which anelectron acceptor (acceptor) is added to an organic compound having ahigh hole-transport property or a structure in which an electron donor(donor) is added to an organic compound having a high electron-transportproperty. Alternatively, both of these structures may be stacked.

In the case of the structure in which an electron acceptor is added toan organic compound having a high hole-transport property, examples ofthe organic compound having a high hole-transport property are aromaticamine compounds such as NPB, TPD, TDATA, MTDATA, and4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB). The substances given here are mainly substanceshaving a hole mobility of 10⁻⁶ cm²/Vs or higher. Note that any othersubstances may also be used as long as the substances havehole-transport properties higher than electron-transport properties.Note that the anthracene compound described in Embodiment 1 can also beused as the organic compound having a high hole-transport property inthe charge-generation layer 305.

Further, examples of the electron acceptor include7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:F₄-TCNQ) and chloranil. Other examples include transition metal oxides.Other examples include oxides of metals belonging to Group 4 to Group 8of the periodic table. Specifically, vanadium oxide, niobium oxide,tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide,manganese oxide, and rhenium oxide are preferable because of their highelectron accepting properties. Among these, molybdenum oxide isespecially preferable because it is stable in the air, has a lowhygroscopic property, and is easily handled.

On the other hand, in the case of the structure in which an electrondonor is added to an organic compound having a high electron-transportproperty, for example, a metal complex having a quinoline skeleton or abenzoquinoline skeleton, such as Alq, Almq₃, BeBq₂, or BAlq, or the likecan be used as the organic compound having a high electron-transportproperty. Alternatively, a metal complex having an oxazole-based ligandor a thiazole-based ligand, such as Zn(BOX)₂ or Zn(BTZ)₂ can be used.Other than metal complexes, PBD, OXD-7, TAZ, BPhen, BCP, or the like canbe used. The substances given here are mainly substances having anelectron mobility of 10⁻⁶ cm²/Vs or higher. Note that any othersubstances may also be used as long as the substances haveelectron-transport properties higher than hole-transport properties. Theanthracene compound described in Embodiment 1 can also be used as theorganic compound having a high electron-transport property.

As the electron donor, an alkali metal, an alkaline earth metal, a rareearth metal, a metal belonging to Group 2 or Group 13 of the periodictable, or an oxide or a carbonate thereof can be used. Specifically,lithium (Li), cesium (Cs), magnesium (Mg), calcium (Ca), ytterbium (Yb),indium (In), lithium oxide, cesium carbonate, or the like is preferablyused. Alternatively, an organic compound such as tetrathianaphthacenemay be used as the electron donor.

Note that forming the charge-generation layer 305 by using any of theabove materials can suppress an increase in drive voltage caused by thestack of the EL layers.

Although the light-emitting element including two EL layers is describedin this embodiment, the present invention can be similarly applied to alight-emitting element in which n EL layers (n is three or more) arestacked as illustrated in FIG. 4B. In the case where a plurality of ELlayers are included between a pair of electrodes as in thelight-emitting element according to this embodiment, by providing thecharge-generation layer between the EL layers, the light-emittingelement can emit light in a high luminance region while the currentdensity is kept low. Since the current density can be kept low, thelight-emitting element can have a long lifetime. When the light-emittingelement is applied to illumination, voltage drop due to resistance of anelectrode material can be reduced, thereby achieving homogeneous lightemission in a large area. In addition, a low power consumptionlight-emitting device, which can be driven at low voltage, can beachieved.

By making the EL layers emit light of different colors from each other,the light-emitting element can provide light emission of a desired coloras a whole. For example, by forming a light-emitting element having twoEL layers such that the emission color of the first EL layer and theemission color of the second EL layer are complementary colors, thelight-emitting element can provide white light emission as a whole. Notethat “complementary colors” refer to colors that can produce anachromatic color when mixed. In other words, when lights obtained fromsubstances which emit light of complementary colors are mixed, whiteemission can be obtained.

The same can be applied to a light-emitting element having three ELlayers. For example, the light-emitting element as a whole can providewhite light emission when the emission color of the first EL layer isred, the emission color of the second EL layer is green, and theemission color of the third EL layer is blue.

Note that the structure described in this embodiment can be used asappropriate in combination with any of the structures described in theother embodiments.

Embodiment 3

In this embodiment, examples of electronic devices and lighting devicesincluding a light-emitting device of one embodiment of the presentinvention are described with reference to FIGS. 5A to 5E and FIGS. 6Aand 6B.

The electronic devices in this embodiment each include thelight-emitting device of one embodiment of the present invention in adisplay portion. The lighting devices in this embodiment each includethe light-emitting device of one embodiment of the present invention ina light-emitting portion (lighting portion). An electronic device and alighting device with low power consumption can be obtained by using thelight-emitting device of one embodiment of the present invention.

Examples of the electronic devices to which the light-emitting device isapplied include television devices (also referred to as TV or televisionreceivers), monitors for computers and the like, digital cameras,digital video cameras, digital photo frames, mobile phones (alsoreferred to as cellular phones or mobile phone devices), portable gamemachines, portable information terminals, audio playback devices, andlarge-sized game machines such as pachinko machines. Specific examplesof these electronic devices and lighting devices are illustrated inFIGS. 5A to 5E and FIGS. 6A and 6B.

FIG. 5A illustrates an example of a television device. In a televisiondevice 7100, a display portion 7102 is incorporated in a housing 7101.Images can be displayed on the display portion 7102. The light-emittingdevice of one embodiment of the present invention can be used for thedisplay portion 7102. In addition, here, the housing 7101 is supportedby a stand 7103.

The television device 7100 can be operated with an operation switch ofthe housing 7101 or a separate remote controller 7111. With operationkeys of the remote controller 7111, channels and volume can becontrolled and images displayed on the display portion 7102 can becontrolled. The remote controller 7111 may be provided with a displayportion for displaying data output from the remote controller 7111.

Note that the television device 7100 is provided with a receiver, amodem, and the like. With the use of the receiver, general televisionbroadcasting can be received. Moreover, when the television device isconnected to a communication network with or without wires via themodem, one-way (from a sender to a receiver) or two-way (between asender and a receiver or between receivers) information communicationcan be performed.

FIG. 5B illustrates an example of a computer. A computer 7200 includes amain body 7201, a housing 7202, a display portion 7203, a keyboard 7204,an external connection port 7205, a pointing device 7206, and the like.Note that the computer 7200 is manufactured by using the light-emittingdevice of one embodiment of the present invention for the displayportion 7203.

FIG. 5C illustrates an example of a portable game machine. A portablegame machine 7300 has two housings, a housing 7301 a and a housing 7301b, which are connected with a joint portion 7302 so that the portablegame machine can be opened and closed. The housing 7301 a incorporates adisplay portion 7303 a, and the housing 7301 b incorporates a displayportion 7303 b. In addition, the portable game machine illustrated inFIG. 5C includes a speaker portion 7304, a recording medium insertionportion 7305, operation keys 7306, a connection terminal 7307, a sensor7308 (a sensor having a function of measuring force, displacement,position, speed, acceleration, angular velocity, rotational frequency,distance, light, liquid, magnetism, temperature, chemical substance,sound, time, hardness, electric field, current, voltage, electric power,radiation, flow rate, humidity, gradient, vibration, smell, or infraredray), an LED lamp, a microphone, and the like. Needless to say, thestructure of the portable game machine is not limited to the above aslong as the light-emitting device of one embodiment of the presentinvention is used for at least either the display portion 7303 a or thedisplay portion 7303 b, or both of them. The portable game machine maybe provided with other accessories as appropriate. The portable gamemachine illustrated in FIG. 5C has a function of reading a program ordata stored in a recording medium to display it on the display portion,and a function of sharing data with another portable game machine bywireless communication. Note that functions of the portable game machineillustrated in FIG. 5C are not limited to the above, and the portablegame machine can have a variety of functions.

FIG. 5D illustrates an example of a mobile phone. A mobile phone 7400includes a display portion 7402 incorporated in a housing 7401,operation buttons 7403, an external connection port 7404, a speaker7405, a microphone 7406, and the like. Note that the mobile phone 7400is manufactured by using the light-emitting device of one embodiment ofthe present invention for the display portion 7402.

When the display portion 7402 of the mobile phone 7400 illustrated inFIG. 5D is touched with a finger or the like, data can be input into themobile phone 7400. Further, operations such as making a call andcreating an e-mail can be performed by touch on the display portion 7402with a finger or the like.

There are mainly three screen modes of the display portion 7402. Thefirst mode is a display mode mainly for displaying an image. The secondmode is an input mode mainly for inputting data such as characters. Thethird mode is a display-and-input mode in which two modes of the displaymode and the input mode are combined.

For example, in the case of making a call or composing an e-mail, a textinput mode mainly for inputting text is selected for the display portion7402 so that text displayed on the screen can be input.

When a sensing device including a sensor such as a gyroscope sensor oran acceleration sensor for detecting inclination is provided inside themobile phone 7400, display on the screen of the display portion 7402 canbe automatically changed in direction by determining the orientation ofthe mobile phone 7400 (whether the mobile phone 7400 is placedhorizontally or vertically for a landscape mode or a portrait mode).

The screen modes are switched by touch on the display portion 7402 oroperation with the operation button 7403 of the housing 7401. The screenmodes can be switched depending on the kind of images displayed on thedisplay portion 7402. For example, when a signal of an image displayedon the display portion is a signal of moving image data, the screen modeis switched to the display mode. When the signal is a signal of textdata, the screen mode is switched to the input mode.

Moreover, in the input mode, when input by touch on the display portion7402 is not performed within a specified period while a signal detectedby an optical sensor in the display portion 7402 is detected, the screenmode may be controlled so as to be switched from the input mode to thedisplay mode.

The display portion 7402 may function as an image sensor. For example,an image of a palm print, a fingerprint, or the like is taken by touchon the display portion 7402 with the palm or the finger, wherebypersonal authentication can be performed. Further, when a backlight or asensing light source which emits near-infrared light is provided in thedisplay portion, an image of a finger vein, a palm vein, or the like canbe taken.

FIG. 5E illustrates an example of a foldable tablet terminal (which isunfolded). A tablet terminal 7500 includes a housing 7501 a, a housing7501 b, a display portion 7502 a, and a display portion 7502 b. Thehousing 7501 a and the housing 7501 b are connected by a hinge 7503 andcan be opened and closed using the hinge 7503 as an axis. The housing7501 a includes a power switch 7504, operation keys 7505, a speaker7506, and the like. Note that the tablet terminal 7500 is manufacturedby using the light-emitting device of one embodiment of the presentinvention for either the display portion 7502 a or the display portion7502 b, or both of them.

At least part of the display portion 7502 a or the display portion 7502b can be used as a touch panel region, where data can be input bytouching displayed operation keys. For example, the entire area of thedisplay portion 7502 a can display keyboard buttons and serve as a touchpanel while the display portion 7502 b is used as a display screen.

An indoor lighting device 7601, a roll-type lighting device 7602, a desklamp 7603, and a planar lighting device 7604, which are illustrated inFIG. 6A, are each an example of a lighting device including thelight-emitting device of one embodiment of the present invention. Thelight-emitting device of one embodiment of the present invention canhave a larger area and thus can be used as a lighting device having alarge area. In addition, the light-emitting device is thin and thus canbe mounted on a wall.

A desk lamp illustrated in FIG. 6B includes a lighting portion 7701, asupport 7703, a support base 7705, and the like. The light-emittingdevice of one embodiment of the present invention is used for thelighting portion 7701. In one embodiment of the present invention, alighting device whose light-emitting portion has a curved surface or alighting device including a flexible lighting portion can be achieved.The use of a flexible light-emitting device for a lighting device asdescribed above not only improves the degree of freedom in design of thelighting device but also enables the lighting device to be mounted ontoa portion having a curved surface, such as the ceiling or a dashboard ofa car.

This embodiment can be combined with any of the other embodiments asappropriate.

Example 1 Synthesis Example 1

In this example, a specific example of a method for synthesizing2′-(3,5-diphenyl)phenyl-dispiro[9H-fluorene-9,9′(10′H)-anthracene-10′,9″-(9H)fluorene](abbreviation:2mTPDfha), which is one embodiment of the anthracene compound describedin Embodiment 1, is described. Note that Structural Formula (100) of2mTPDfha (abbreviation) is shown below.

In a 100 ml three-neck flask were put 1.4 g (2.4 mmol) of2′-bromo-dispiro[9H-fluorene-9,9′(10′H)-anthracene-10′,9″-(9H)-fluorene](abbreviation:2BrDfha), 0.80 g (2.9 mmol) of (3,5-diphenylphenyl)boronic acid, and 89mg (292 μmol) of tris(2-methylphenyl)phosphine, and the air in the flaskwas replaced with nitrogen. Then, 30 ml of toluene, 2.9 ml of ethanol,and 2.9 ml of a 2M aqueous solution of potassium carbonate (810 mg ofpotassium carbonate) were added thereto, and the mixture was degassedwhile being stirred under reduced pressure. Then, 32 mg (150 μmol) ofpalladium acetate was added thereto, and the mixture was stirred at 85°C. under a nitrogen stream for 8 hours. Then, 89 mg (290 μmol) oftris(2-methylphenyl)phosphine and 33 mg (150 μmol) of palladium acetatewere added thereto, and the mixture was stirred at 85° C. for 5 hours.Then, 200 mg (730 μmol) of (3,5-diphenylphenyl)boronic acid, 270 mg (880μmol) of tris(2-methylphenyl)phosphine, and 98 mg (440 μmol) ofpalladium acetate were added thereto, and the mixture was stirred at 85°C. under a nitrogen stream for 9.5 hours. After the stirring for apredetermined time, toluene was added to the mixture and the mixture wasfiltered with diatomaceous earth. Water was added to the obtainedfiltrate, and extraction with toluene was performed to obtain an organiclayer. The obtained organic layer was washed with saturated saline, andmagnesium sulfate was added thereto. The mixture was gravity-filtered,and the obtained filtrate was condensed to give a yellow solid. Theobtained yellow solid was purified by silica gel column chromatography(from a mixed solution of toluene and hexane to a mixed solution ofethyl acetate and hexane) to give a fraction including a targetsubstance and a fraction including a target substance mixed with animpurity. The fraction including the target substance was condensed, amixed solution of hexane and acetone was added thereto, the mixture wasirradiated with ultrasonic waves, and the mixture was subjected tosuction filtration to give 650 mg of a white solid, which was a targetsubstance, in a yield of 38%. The fraction including the targetsubstance mixed with the impurity was condensed, dissolved inapproximately 40 ml of hot toluene, and approximately 10 ml of hexanewas added thereto to perform recrystallization, so that a white solidwas obtained. A mixed solution of hexane and acetone was added to theobtained white solid, the mixture was irradiated with ultrasonic waves,and the mixture was subjected to suction filtration to give 390 mg of awhite solid, which was a target substance, in a yield of 22%. Theobtained substance was 1.0 g in total, and the yield was 60%. SynthesisScheme (a-1) of this synthesis is shown below.

¹H NMR (300 MHz, CDCl₃) data of the obtained substance are as follows.¹H NMR (300 MHz, CDCl₃): δ (ppm)=6.40-6.45 (m, 2H), 6.50 (d, J=8.4 Hz,1H), 6.65 (d, J=1.8 Hz, 1H), 6.77-6.82 (m, 2H), 7.08 (dd, J=1.8 Hz, 8.3Hz, 1H), 7.25-7.50 (m, 24H), 7.60 (t, J=1.5 Hz, 1H), 7.90-7.96 (m, 4H).

FIGS. 8A and 8B show ¹H NMR (300 MHz, CDCl₃) data of the obtainedsubstance. FIG. 8B is a chart where the range of from 6 ppm to 9 ppm inFIG. 8A is enlarged.

An ultraviolet-visible absorption spectrum (hereinafter, simply referredto as absorption spectrum) and an emission spectrum of2′-(3,5-diphenyl)phenyl-dispiro[9H-fluorene-9,9′(10′H)-anthracene-10′,9″-(9H)fluorene](abbreviation:2mTPDfha) in a toluene solution were measured. The absorption spectrumwas measured at room temperature with the use of an ultraviolet-visiblelight spectrophotometer (V-550, manufactured by JASCO Corporation) in astate where a toluene solution was put in a quartz cell. The emissionspectrum was measured with the use of a fluorescence spectrophotometer(FS920, manufactured by Hamamatsu Photonics Corporation) in a statewhere a degassed toluene solution was put in a quartz cell at roomtemperature. As for the measurement of the absorption spectrum of a thinfilm, the absorption spectrum was obtained as follows: the thin filmthat was formed by evaporation on a quartz substrate was used and anabsorption spectrum of quartz was subtracted from absorption spectra ofthe thin film and the quartz.

In the case of the toluene solution of 2mTPDfha (abbreviation), theabsorption peak was observed at around 311 nm. In the case of the thinfilm of 2mTPDfha (abbreviation), the absorption peak was observed ataround 312 nm.

Further, in the case of the toluene solution of 2mTPDfha (abbreviation),the maximum emission wavelength was 350 nm (excitation wavelength: 270nm). In the case of the thin film of 2mTPDfha (abbreviation), themaximum emission wavelength was 353 nm (excitation wavelength: 312 nm).

The above results demonstrate that 2mTPDfha (abbreviation) of oneembodiment of the present invention has a high S₁ level and emitsultraviolet fluorescence.

Next, 2mTPDfha (abbreviation) was subjected to cyclic voltammetry (CV)measurement. An electrochemical analyzer (ALS model 600A or 600C,manufactured by BAS Inc.) was used for the CV measurement.

Further, as for a solution used for the CV measurements, dehydrateddimethylformamide (DMF, produced by Sigma-Aldrich Inc., 99.8%, CatalogNo. 22705-6) was used as a solvent, and tetra-n-butylammoniumperchlorate (n-Bu₄NClO₄, produced by Tokyo Chemical Industry Co., Ltd.,Catalog No. T0836), which was a supporting electrolyte, was dissolved inthe solvent such that the concentration of tetra-n-butylammoniumperchlorate was 100 mmol/L. Further, the object to be measured wasdissolved in the solvent such that the concentration thereof was 2mmol/L. A platinum electrode (PTE platinum electrode, produced by BASInc.) was used as a working electrode, another platinum electrode (Ptcounter electrode for VC-3 (5 cm), produced by BAS Inc.) was used as anauxiliary electrode, and an Ag/Ag⁺ electrode (RE7 reference electrodefor nonaqueous solvent, produced by BAS Inc.) was used as a referenceelectrode. The CV measurement was performed under the followingconditions: room temperature (20° C. to 25° C.) and a scan rate of 0.1V/sec. Note that the potential energy of the reference electrode withrespect to the vacuum level was assumed to be −4.94 eV in this example.

The LUMO level of 2mTPDfha (abbreviation) was obtained from the CVmeasurement results. From a reduction peak potential (from the neutralstate to the reduction state) E_(pa) [V] and an oxidation peak potential(from the reduction state to the neutral state) E_(pc) [V], a half wavepotential (a potential between E_(pa) and E_(pc)) was calculated to be−2.75 eV ((E_(pa)+E_(pc))/2 [V]=−2.75 eV). Then, a half wave potentialof −2.75 eV was subtracted from a potential energy of the referenceelectrode with respect to the vacuum level of −4.94 eV to obtain a LUMOlevel (a reduction potential) of −2.20 eV.

The above results demonstrate that 2mTPDfha (abbreviation) of oneembodiment of the present invention has a relatively shallow LUMO level.

Furthermore, mass spectrometry (MS) of 2mTPDfha (abbreviation) wascarried out by liquid chromatography mass spectrometry (LC/MS).

The analysis by LC/MS was carried out with Acquity UPLC (produced byWaters Corporation) and Xevo G2 Tof MS (produced by Waters Corporation).ACQUITY UPLC BEH C8 (2.1×100 mm, 1.7 μm) was used as a column for the LCseparation, and the column temperature was 40° C. Acetonitrile was usedfor Mobile Phase A and 0.1 volume % of a formic acid aqueous solutionwas used for Mobile Phase B. Further, a sample was prepared in such amanner that 2mTPDfha (abbreviation) was dissolved in toluene at a givenconcentration and the mixture was diluted with acetonitrile. Theinjection amount was 5.0 μL.

In the MS analysis, ionization was carried out by an electrosprayionization (ESI) method. At this time, the capillary voltage and thesample cone voltage were set to 3.0 kV and 30 V, respectively, anddetection was performed in a positive mode. A component with m/z of709.29 that underwent the ionization under the above-describedconditions was collided with an argon gas in a collision cell todissociate into product ions. Energy (collision energy) for thecollision with argon was 70 eV. The mass range for the measurement wasm/z=100 to 1200. The detection results of the dissociated product ionsby time-of-flight (TOF) MS are shown in FIGS. 9A and 9B. FIG. 9B isobtained by increasing the scale of the vertical axis of FIG. 9A.

The results in FIGS. 9A and 9B show that the product ion of 2mTPDfha(abbreviation) is detected mainly around m/z=403.15. Note that theresults in FIGS. 9A and 9B show characteristics derived from 2mTPDfha(abbreviation) and therefore can be regarded as important data foridentifying 2mTPDfha (abbreviation) contained in the mixture.

Note that the product ion around m/z=403.15 is presumed to be a radicalcation in the state (C₃₂H₁₉) where a benzene skeleton is dissociatedfrom 2mTPDfha (abbreviation).

Example 2 Synthesis Example 2

In this example, a specific example of a method for synthesizing9-(3-{dispiro[9H-fluorene-9,9′(10′H)-anthracene-10′,9″-(9H)fluorene]2′-yl}phenyl)-9H-carbazole(abbreviation: 2mCzPDfha), which is one embodiment of the anthracenecompound described in Embodiment 1, is described. Note that StructuralFormula (103) of 2mCzPDfha (abbreviation) is shown below.

In a 100 ml three-neck flask were put 1.25 g (2.23 mmol) of2′-bromo-dispiro[9H-fluorene-9,9′(10′H)-anthracene-10′,9″-(9H)-fluorene](abbreviation:2BrDfha), 770 mg (2.68 mmol) of 3-(carbazol-9-yl)phenylboronic acid, and81.6 mg (268 μmol) of tris(2-methylphenyl)phosphine, and the air in theflask was replaced with nitrogen. Then, 30 ml of toluene, 2.7 ml ofethanol, and 2.7 ml of a 2M aqueous solution of potassium carbonate (741mg of potassium carbonate) were added thereto, and the mixture wasdegassed while being stirred under reduced pressure. Then, 30.1 mg (134μmol) of palladium acetate was added thereto, and the mixture wasstirred at 85° C. under a nitrogen stream for 8 hours. Then, 81.6 mg(268 μmol) of tris(2-methylphenyl)phosphine and 30.1 mg (134 μmol) ofpalladium acetate were added thereto, and the mixture was stirred at 85°C. for 5 hours. Then, 201 mg (699 μmol) of3-(carbazol-9-yl)phenylboronic acid, 245 mg (804 μmol) oftris(2-methylphenyl)phosphine, and 90.3 mg (402 μmol) of palladiumacetate were added thereto, and the mixture was stirred at 85° C. undera nitrogen stream for 9.5 hours. After the stirring for a predeterminedtime, toluene was added to the mixture and the mixture was filtered withdiatomaceous earth. Then, water was added to the obtained filtrate andextraction with toluene was performed to obtain an organic layer. Theobtained organic layer was washed with saturated saline, and magnesiumsulfate was added thereto so that moisture was adsorbed. The mixture wasgravity-filtered and the filtrate was condensed, followed bypurification by silica gel column chromatography (toluene, a mixedsolution of toluene and hexane, and a mixed solution of ethyl acetateand hexane were used) to give a white solid. A mixed solution of hexaneand acetone was added to the obtained white solid, and the resultingsuspension was subjected to suction filtration to give 0.99 g of a whitesolid, which was a target substance, in a yield of 61.4%. SynthesisScheme (a-2) of this synthesis is shown below.

¹H NMR data of the obtained substance are as follows.

¹H NMR (300 MHz, CDCl₃): δ (ppm)=6.38-6.52 (m, 3H), 6.64-6.69 (m, 1H),6.76-6.85 (m, 2H), 7.04 (dd, J=2.4 Hz, 8.4 Hz, 1H), 7.09-7.17 (m, 1H),7.21-7.49 (m, 21H), 7.93 (d, J=7.2 Hz, 4H), 8.10 (d, J=7.8 Hz, 2H).

FIGS. 10A and 10B show ¹H NMR (300 MHz, CDCl₃) data of the obtainedsubstance. FIG. 10B is a chart where the range of from 6 ppm to 8.5 ppmin FIG. 10A is enlarged.

An ultraviolet-visible absorption spectrum and an emission spectrum of9-(3-{dispiro[9H-fluorene-9,9′(10′H)-anthracene-10′,9″-(9H)fluorene]2′-yl}phenyl)-9H-carbazole(abbreviation: 2mCzPDfha) in a toluene solution were measured. Theabsorption spectrum was measured at room temperature with the use of anultraviolet-visible light spectrophotometer (V-550, manufactured byJASCO Corporation) in a state where a toluene solution was put in aquartz cell. The emission spectrum was measured with the use of afluorescence spectrophotometer (FS920, manufactured by HamamatsuPhotonics Corporation) in a state where a degassed toluene solution wasput in a quartz cell at room temperature. As for the measurement of theabsorption spectrum of a thin film, the absorption spectrum was obtainedas follows: the thin film that was formed by evaporation on a quartzsubstrate was used and an absorption spectrum of quartz was subtractedfrom absorption spectra of the thin film and quartz.

In the case of the toluene solution of 2mCzPDfha (abbreviation), theabsorption peak was observed at around 341 nm. In the case of the thinfilm of 2mCzPDfha (abbreviation), the absorption peak was observed ataround 343 nm.

Further, in the case of the toluene solution of 2mCzPDfha(abbreviation), the emission peaks were observed at 362 nm and 347 nm(excitation wavelength: 290 nm), and the maximum emission wavelength was347 nm. In the case of the thin film of 2mCzPDfha (abbreviation), theemission peaks were observed at 450 nm, 424 nm, 366 nm, and 351 nm(excitation wavelength: 344 nm), and the maximum emission wavelength was351 nm.

The above results demonstrate that 2mCzPDfha (abbreviation) of oneembodiment of the present invention has a high S₁ level and emits purplefluorescence.

Next, 2mCzPDfha (abbreviation) was subjected to cyclic voltammetry (CV)measurement. An electrochemical analyzer (ALS model 600A or 600C,manufactured by BAS Inc.) was used for the CV measurement.

Further, as for a solution used for the CV measurements, dehydrateddimethylformamide (DMF, produced by Sigma-Aldrich Inc., 99.8%, CatalogNo. 22705-6) was used as a solvent, and tetra-n-butylammoniumperchlorate (n-Bu₄NClO₄, produced by Tokyo Chemical Industry Co., Ltd.,Catalog No. T0836), which was a supporting electrolyte, was dissolved inthe solvent such that the concentration of tetra-n-butylammoniumperchlorate was 100 mmol/L. Further, the object to be measured wasdissolved in the solvent such that the concentration thereof was 2mmol/L. A platinum electrode (PTE platinum electrode, produced by BASInc.) was used as a working electrode, another platinum electrode (Ptcounter electrode for VC-3 (5 cm), produced by BAS Inc.) was used as anauxiliary electrode, and an Ag/Ag⁺ electrode (RE7 reference electrodefor nonaqueous solvent, produced by BAS Inc.) was used as a referenceelectrode. The CV measurement was performed under the followingconditions: room temperature (20° C. to 25° C.) and a scan rate of 0.1V/sec. Note that the potential energy of the reference electrode withrespect to the vacuum level was assumed to be −4.94 eV in this example.

The LUMO level of 2mCzPDfha (abbreviation) was obtained from the CVmeasurement results. From a reduction peak potential (from the neutralstate to the reduction state) E_(pa) [V] and an oxidation peak potential(from the reduction state to the neutral state) E_(pc) [V], a half wavepotential (a potential between E_(pa) and E_(pc)) was calculated to be−2.78 eV ((E_(pa)+E_(pc))/2 [V]=−2.78 eV). Then, a half wave potentialof −2.78 eV was subtracted from a potential energy of the referenceelectrode with respect to the vacuum level of −4.94 eV to obtain a LUMOlevel (a reduction potential) of −2.16 eV.

Next, the HOMO level (oxidation potential) of 2mCzPDfha (abbreviation)was obtained from the CV measurement results. Scan was performed to theoxidation side (0.2 eV to 1.0 eV) to obtain a HOMO level of −5.90 eV.

The above results demonstrate that 2mCzPDfha (abbreviation) of oneembodiment of the present invention has a relatively shallow LUMO leveland a relatively deep HOMO level.

Furthermore, mass spectrometry (MS) of 2mCzPDfha (abbreviation) wascarried out by liquid chromatography mass spectrometry (LC/MS).

The analysis by LC/MS was carried out with Acquity UPLC (produced byWaters Corporation) and Xevo G2 Tof MS (produced by Waters Corporation).ACQUITY UPLC BEH C8 (2.1×100 mm, 1.7 μm) was used as a column for the LCseparation, and the column temperature was 40° C. Acetonitrile was usedfor Mobile Phase A and 0.1 volume % of a formic acid aqueous solutionwas used for Mobile Phase B. Further, a sample was prepared in such amanner that 2mCzPDfha (abbreviation) was dissolved in toluene at a givenconcentration and the mixture was diluted with acetonitrile. Theinjection amount was 5.0 μL.

In the MS analysis, ionization was carried out by an electrosprayionization (ESI) method. At this time, the capillary voltage and thesample cone voltage were set to 3.0 kV and 30 V, respectively, anddetection was performed in a positive mode. A component with m/z of722.29 that underwent the ionization under the above-describedconditions was collided with an argon gas in a collision cell todissociate into product ions. Energy (collision energy) for thecollision with argon was 50 eV. The mass range for the measurement wasm/z=100 to 1200. The detection results of the dissociated product ionsby time-of-flight (TOF) MS are shown in FIG. 11.

The results in FIG. 11 show that the product ions of 2mCzPDfha(abbreviation) are detected mainly around m/z=556.12 and aroundm/z=403.15. Note that the results in FIG. 11 show characteristicsderived from 2mCzPDfha (abbreviation) and therefore can be regarded asimportant data for identifying 2mCzPDfha (abbreviation) contained in themixture.

The product ion detected around m/z=556.12 is presumed to be a radicalcation in the state (C₄₄H₂₈) where a carbazolyl group is dissociatedfrom 2mCzPDfha (abbreviation), which means that 2mCzPDfha (abbreviation)contains a carbazolyl group.

The product ion detected around m/z=403.15 is presumed to be a cation inthe state (C₃₂H₁₉) where a carbazolyl group and two benzene skeletonsare dissociated from 2mCzPDfha (abbreviation).

Example 3 Synthesis Example 3

In this example, a specific example of a method for synthesizing2-(3-{dispiro[9H-fluorene-9,9′(10′H)-anthracene-10′,9″-(9H)fluoren]2′-yl}phenyl)dibenzo[f,h]quinoxaline(abbreviation: 2mDBqPDfha), which is one embodiment of the anthracenecompound described in Embodiment 1, is described. Note that StructuralFormula (112) of 2mDBqPDfha (abbreviation) is shown below.

In a 100 ml three-neck flask were put 1.23 g (3.20 mmol) of2-(3-bromophenyl)dibenzo[f,h]quinoxaline, 1.85 g (3.52 mmol) ofdispiro[9H-fluorene-9,9′(10′H)-anthracene-10′,9″-(9H)fluorene]-2-boronicacid, and 42.9 mg (141 μmol) of tris(2-methylphenyl)phosphine, and theair in the flask was replaced with nitrogen. Then, 35 ml of toluene, 3.5ml of ethanol, and 3.52 ml (7.04 mmol) of a 2M aqueous solution ofpotassium carbonate were added thereto, and the mixture was degassed.The degassed mixture was stirred and heated at 85° C. for 25 hours while47.7 mg (0.21 mmol) of palladium acetate was added thereto in threetimes and 85.8 mg (0.28 mmol) of tris(2-methylphenyl)phosphine was addedthereto in two times. After completion of a reaction, toluene was addedthereto to control the amount of liquid to 350 ml and the mixture washeated. Water was added thereto, followed by suction filtration to givea gray solid. Then, 150 ml of toluene was added to the obtained graysolid and the mixture was heated, followed by suction filtration to givea gray solid. Then, 100 ml of toluene was added to the obtained graysolid and the mixture was heated, followed by suction filtration to givea gray solid. Methanol was added to the obtained gray solid and themixture was irradiated with ultrasonic waves, so that the gray solid wassuspended, followed by suction filtration to give 1.84 g of a graysolid, which was a target substance, in a yield of 73.3%. SynthesisScheme (a-3) of this synthesis is shown below.

An absorption spectrum and an emission spectrum of2-(3-{dispiro[9H-fluorene-9,9′(10′H)-anthracene-10′,9″-(9H)fluoren]2′-yl}phenyl)dibenzo[f,h]quinoxaline(abbreviation: 2mDBqPDfha) in a toluene solution were measured. Theabsorption and emission spectra were measured in a manner similar tothat described in Example 1.

The absorption peak of 2mDBqPDfha (abbreviation) in the toluene solutionwas observed at around 376 nm.

The emission peaks of 2mDBqPDfha (abbreviation) in the toluene solutionwere observed at around 408 nm and 487 nm (excitation wavelength: 311nm), and the maximum emission wavelength was 408 nm.

The above results demonstrate that 2mDBqPDfha (abbreviation) of oneembodiment of the present invention has a high S₁ level and emits purplefluorescence.

The phosphorescence spectrum of 2mDBqPDfha (abbreviation) was measuredby low-temperature PL spectroscopy. The measurement was performed byusing a PL microscope, LabRAM HR-PL, produced by HORIBA, Ltd., a He—Cdlaser (325 nm) as excitation light, and a CCD detector at a measurementtemperature of 10 K. For the measurement, a thin film of 2mDBqPDfha(abbreviation) was formed over a quartz substrate to a thickness of 30nm and another quartz substrate was attached to the deposition surfacein a nitrogen atmosphere. Measurement results demonstrate that2mDBqPDfha (abbreviation) has a phosphorescence peak at 515 nm and a T₁level high enough to serve as a host material for a green phosphorescentmaterial.

Next, 2mDBqPDfha (abbreviation) was subjected to cyclic voltammetry (CV)measurement. An electrochemical analyzer (ALS model 600A or 600C,manufactured by BAS Inc.) was used for the CV measurement. Themeasurement was performed in a manner similar to that described inExample 1.

The LUMO level (reduction potential) of 2mDBqPDfha (abbreviation) wascalculated from the CV measurement results to be −2.93 eV.

The above results demonstrate that 2mDBqPDfha (abbreviation) of oneembodiment of the present invention has a relatively deep LUMO level.

Furthermore, the ionization potential of 2mDBqPDfha (abbreviation) in athin film state was measured by a photoelectron spectrometer (AC-3produced by Riken Keiki, Co., Ltd.) in the atmosphere. The obtainedvalue of the ionization potential was converted into a negative value,so that the HOMO level of 2mDBqPDfha (abbreviation) was −6.51 eV. Fromthe data of the absorption spectra of the thin film, the absorption edgeof 2mDBqPDfha (abbreviation), which was obtained from Tauc plot with anassumption of direct transition, was 3.11 eV. Therefore, the opticalenergy gap of 2mDBqPDfha (abbreviation) in the solid state was estimatedat 3.11 eV; from the values of the HOMO level obtained above and thisenergy gap, the LUMO level of 2mDBqPDfha (abbreviation) was able to beestimated at −3.4 eV. It was thus found that 2mDBqPDfha (abbreviation)in the solid state has a relatively deep HOMO and LUMO levels and a wideenergy gap of 3.11 eV.

Furthermore, mass spectrometry (MS) of 2mDBqPDfha (abbreviation) wascarried out by liquid chromatography mass spectrometry (LC/MS). Themeasurement was performed in a manner similar to that described inExample 1.

The detection results of the dissociated product ions by time-of-flight(TOF) MS are shown in FIGS. 37A and 37B.

The results in FIGS. 37A and 37B show that the product ions of2mDBqPDfha (abbreviation) are detected mainly around m/z=785, aroundm/z=403, and around m/z=631. Note that the results in FIGS. 37A and 37Bshow characteristics derived from 2mDBqPDfha (abbreviation) andtherefore can be regarded as important data for identifying 2mDBqPDfha(abbreviation) contained in the mixture.

Note that the product ion around m/z=631 is presumed to be a radicalcation in the state (C₄₈H₂₇) where two benzene skeletons are dissociatedfrom 2mDBqPDfha (abbreviation).

Further, the product ion around m/z=403 is presumed to be a cation inthe state (C₃₂H₁₉) where a 2-phenyl-dibenzo[f,h]quinoxalinyl group andone benzene skeleton are dissociated from 2mDBqPDfha (abbreviation).

Example 4

In this example, a light-emitting element 1 that is one embodiment ofthe present invention is described with reference to FIG. 7. Shown beloware molecular structures of organic compounds used in this example.

<<Manufacture of Light-Emitting Element>>

First, a glass substrate over which a film of indium tin oxidecontaining silicon (ITSO) with a thickness of 110 nm had been formed asan anode 1101 was prepared. A surface of the ITSO was covered with apolyimide film so that an area of 2 mm×2 mm of the surface was exposed.As pretreatment for forming the light-emitting element over thesubstrate, the surface of the substrate was washed with water and bakedat 200° C. for 1 hour, and then UV ozone treatment was performed for 370seconds. Then, the substrate was transferred into a vacuum evaporationapparatus where the pressure had been reduced to about 10⁻⁴ Pa, vacuumbaking at 170° C. for 30 minutes was performed in a heating chamber ofthe vacuum evaporation apparatus, and then the substrate was cooled downfor about 30 minutes.

Next, the substrate was fixed to a holder provided in the vacuumevaporation apparatus so that a surface of the substrate provided withthe anode 1101 was faced downward.

After reducing the pressure of the vacuum evaporation apparatus to 10⁻⁴Pa, 1,3,5-tri(dibenzothiophen-4-yl)benzene (abbreviation: DBT3P-II) andmolybdenum(VI) oxide were deposited by co-evaporation so that the weightratio of DBT3P-II to molybdenum oxide was 2:1, whereby a hole-injectionlayer 1107 was formed. The thickness of the hole-injection layer 1107was 40 nm. Note that the co-evaporation is an evaporation method inwhich a plurality of different substances are concurrently vaporizedfrom the respective evaporation sources.

Next, a film of 9-phenyl-9H-3-(9-phenyl-9H-carbazol-3-yl)carbazole(abbreviation: PCCP) was formed to a thickness of 20 nm by evaporation,whereby a hole-transport layer 1103 was formed.

Then, on the hole-transport layer 1103,2′-(3,5-diphenyl)phenyl-dispiro[9H-fluorene-9,9′(10′H)-anthracene-10′,9″-(9H)fluorene](abbreviation:2mTPDfha) that is the anthracene compound described in Embodiment 1 andtris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III)(abbreviation: [Ir(Mptz)₃]) were deposited to a thickness of 30 nm byevaporation so that the weight ratio of 2mTPDfha to [Ir(Mptz)₃] was1:0.06, and then2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole(abbreviation: mDBTBIm-II) andtris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(Mptz1-mp)₃]) were deposited thereon to a thickness of10 nm by evaporation so that the weight ratio of mDBTBIm-II to[Ir(Mptz1-mp)₃] was 1:0.06, whereby a light-emitting layer 1104 wasformed.

Next, bathophenanthroline (abbreviation: BPhen) was deposited to athickness of 20 nm by evaporation, whereby an electron-transport layer1105 was formed.

Furthermore, lithium fluoride was deposited to a thickness of 1 nm onthe electron-transport layer 1105 by evaporation, whereby anelectron-injection layer 1108 was formed. Lastly, a 200-nm-thickaluminum film was formed as a cathode 1102. Thus, the light-emittingelement was manufactured. Note that in all the above evaporation steps,evaporation was performed by a resistance-heating method.

The element structure of the manufactured light-emitting element 1 isshown below.

TABLE 1 Hole- Hole- Electron- Electron- Functional injection transporttransport injection layer layer layer Light-emitting layer layer layerLight-emitting Thickness 40 nm 20 nm 30 nm 10 nm 20 nm 1 nm element 1Structure DBT3P-II:MoOx = PCCP 2mTPDfha:[Ir(Mptz)₃] =mDBTBIm-II:[Ir(Mptz1- BPhen LiF 2:1 1:0.06 mp)₃] = 1:0.06 Anode: 110 nmITSO Cathode: 200 nm Al<<Operation Characteristics of Light-Emitting Element>>

The light-emitting element 1 thus obtained was sealed in a glove boxunder a nitrogen atmosphere without being exposed to the air. Then, theoperation characteristics of the light-emitting element 1 were measured.Note that the measurement was carried out at room temperature (in anatmosphere kept at 25° C.).

FIG. 12 shows current density-luminance characteristics of thelight-emitting element 1. In FIG. 12, the vertical axis representsluminance (cd/m²) and the horizontal axis represents current density(mA/cm²). FIG. 13 shows voltage-luminance characteristics of thelight-emitting element 1. In FIG. 13, the vertical axis representsluminance (cd/m²) and the horizontal axis represents voltage (V). FIG.14 shows luminance-current efficiency characteristics of thelight-emitting element 1. In FIG. 14, the vertical axis representscurrent efficiency (cd/A) and the horizontal axis represents luminance(cd/m²). FIG. 15 shows voltage-current characteristics of thelight-emitting element 1. In FIG. 15, the vertical axis representscurrent (mA) and the horizontal axis represents voltage (V). FIG. 16shows chromaticity characteristics of the light-emitting element 1. InFIG. 16, the vertical axis represents chromaticity and the horizontalaxis represents luminance.

FIG. 12 demonstrates that the use of 2mTPDfha (abbreviation) that is oneembodiment of the present invention for a light-emitting layer enables ahighly efficient element to be obtained. According to FIG. 16, thelight-emitting element 1 has a small change in chromaticity that dependson luminance and has excellent carrier balance. In addition, excellentchromaticity can be obtained and 2mTPDfha (abbreviation) that is oneembodiment of the present invention is suitable as a host material foran element emitting phosphorescence in the blue region because 2mTPDfha(abbreviation) has a high T₁ level. Table 2 shows initial values of maincharacteristics of the light-emitting element 1 at a luminance ofapproximately 1000 cd/m².

TABLE 2 Current Current Power Voltage Current density ChromaticityLuminance efficiency efficiency (V) (mA) (mA/cm²) (x, y) (cd/m²) (cd/A)(lm/W) Light- 6.2 0.10 2.6 (0.20, 0.40) 880 34 17 emitting element 1

The above results demonstrate that the light-emitting element 1manufactured in this example is a highly efficient element emittingphosphorescence in the blue region.

Example 5

In this example, a light-emitting element 2 that is one embodiment ofthe present invention is described. Note that the light-emitting element2 in this example is described with reference to FIG. 7 that is used fordescribing the light-emitting element 1 in Example 4. Shown below aremolecular structures of organic compounds used in this example.

<<Manufacture of Light-Emitting Element>>

First, a glass substrate over which a film of indium tin oxidecontaining silicon (ITSO) with a thickness of 110 nm had been formed asan anode 1101 was prepared. A surface of the ITSO was covered with apolyimide film so that an area of 2 mm×2 mm of the surface was exposed.As pretreatment for forming the light-emitting element over thesubstrate, the surface of the substrate was washed with water and bakedat 200° C. for 1 hour, and then UV ozone treatment was performed for 370seconds. Then, the substrate was transferred into a vacuum evaporationapparatus where the pressure had been reduced to about 10⁻⁴ Pa, vacuumbaking at 170° C. for 30 minutes was performed in a heating chamber ofthe vacuum evaporation apparatus, and then the substrate was cooled downfor about 30 minutes.

Next, the substrate was fixed to a holder provided in the vacuumevaporation apparatus so that a surface of the substrate provided withthe anode 1101 was faced downward.

After reducing the pressure of the vacuum evaporation apparatus to 10⁻⁴Pa, 4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP) and molybdenum(VI)oxide were deposited by co-evaporation so that the weight ratio of CBPto molybdenum oxide was 2:1, whereby the hole-injection layer 1107 wasformed. The thickness of the hole-injection layer 1107 was 60 nm.

Next,9-(3-{dispiro[9H-fluorene-9,9′(10′H)-anthracene-10′,9″-(9H)fluorene]2′-yl}phenyl)-9H-carbazole(abbreviation: 2mCzPDfha) that is the anthracene compound represented byStructural Formula (103) was deposited to a thickness of 20 nm byevaporation, whereby the hole-transport layer 1103 was formed.

On the hole-transport layer 1103, 2mCzPDfha (abbreviation) that is theanthracene compound represented by Structural Formula (103) andtris(2-phenylpyridinato)iridium(III) (abbreviation: [Ir(ppy)₃]) weredeposited to a thickness of 40 nm by evaporation so that the weightratio of 2mCzPDfha to [Ir(ppy)₃] was 1:0.06, whereby the light-emittinglayer 1104 was formed.

Next, 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole(abbreviation: mDBTBIm-II) was deposited to a thickness of 15 nm byevaporation, and then bathophenanthroline (abbreviation: BPhen) wasdeposited to a thickness of 20 nm by evaporation, whereby theelectron-transport layer 1105 was formed.

Furthermore, lithium fluoride was deposited to a thickness of 1 nm onthe electron-transport layer 1105 by evaporation, whereby anelectron-injection layer 1108 was formed. Lastly, a 200-nm-thickaluminum film was formed as the cathode 1102 functioning as a cathode.Thus, the light-emitting element was manufactured. Note that in all theabove evaporation steps, evaporation was performed by aresistance-heating method.

The element structure of the manufactured light-emitting element 2 isshown below.

TABLE 3 Hole- Electron- Functional injection Hole-transportLight-emitting injection layer layer layer layer Electron-transportlayer layer Light- Thickness 60 nm 20 nm 40 nm 15 nm 20 nm 1 nm emittingStructure CBP:MoOx = 2mCzPDfha 2mCzPDfha:[Ir(ppy)₃] = mDBTBIm-II BPhenLiF element 2 2:1 1:0.06 Anode: 110 nm ITSO Cathode: 200 nm Al<<Operation Characteristics of Light-Emitting Element>>

The light-emitting element 2 thus obtained was sealed in a glove boxunder a nitrogen atmosphere without being exposed to the air. Then, theoperation characteristics of the light-emitting element 2 were measured.Note that the measurement was carried out at room temperature (in anatmosphere kept at 25° C.).

FIG. 17 shows current density-luminance characteristics of thelight-emitting element 2. In FIG. 17, the vertical axis representsluminance (cd/m²) and the horizontal axis represents current density(mA/cm²). FIG. 18 shows voltage-luminance characteristics of thelight-emitting element 2. In FIG. 18, the vertical axis representsluminance (cd/m²) and the horizontal axis represents voltage (V). FIG.19 shows voltage-current characteristics of the light-emitting element2. In FIG. 19, the vertical axis represents current (mA) and thehorizontal axis represents voltage (V). FIG. 20 shows chromaticitycharacteristics of the light-emitting element 2. In FIG. 20, thevertical axis represents chromaticity and the horizontal axis representsluminance.

FIG. 17 demonstrates that the use of 2mCzPDfha (abbreviation) that isone embodiment of the present invention for a hole-transport layer and alight-emitting layer enables a highly efficient element to be obtained.According to FIG. 20, the light-emitting element 2 has a small change inchromaticity that depends on luminance and has excellent carrierbalance. In addition, excellent chromaticity can be obtained and2mCzPDfha (abbreviation) that is one embodiment of the present inventionis suitable as a host material for an element emitting phosphorescencein the green region because 2mCzPDfha (abbreviation) has a high T₁level. Table 4 shows initial values of main characteristics of thelight-emitting element 2 at a luminance of approximately 1000 cd/m².

TABLE 4 Current Current Power Voltage Current density ChromaticityLuminance efficiency efficiency (V) (mA) (mA/cm²) (x, y) (cd/m²) (cd/A)(lm/W) Light- 9.2 0.13 3.4 (0.30, 0.62) 970 29 9.8 emitting element 2

The above results demonstrate that the light-emitting element 2manufactured in this example is a highly efficient element emittinglight in the green region.

FIG. 21 shows an emission spectrum of the light-emitting element 2,which was obtained by applying a current of 0.1 mA to the light-emittingelement 2. In FIG. 21, the vertical axis represents emission intensity(arbitrary unit) and the horizontal axis represents wavelength (nm). Theemission intensity is shown as a value relative to the greatest emissionintensity assumed to be 1. As shown in FIG. 21, the emission spectrum ofthe light-emitting element 2 is a spectrum that has the maximum emissionwavelength at around 509 nm and is derived from [Ir(ppy)₃]. This meansthat the light-emitting element 2 emits green light.

Example 6

In this example, a light-emitting element 3 that is one embodiment ofthe present invention is described. Note that the light-emitting element3 in this example is described with reference to FIG. 7 that is used fordescribing the light-emitting element 1 in Example 4. Shown below aremolecular structures of organic compounds used in this example.

<<Manufacture of Light-Emitting Element>>

First, a glass substrate over which a film of indium tin oxidecontaining silicon (ITSO) with a thickness of 110 nm had been formed asan anode 1101 was prepared. A surface of the ITSO was covered with apolyimide film so that an area of 2 mm×2 mm of the surface was exposed.As pretreatment for forming the light-emitting element over thesubstrate, the surface of the substrate was washed with water and bakedat 200° C. for 1 hour, and then UV ozone treatment was performed for 370seconds. Then, the substrate was transferred into a vacuum evaporationapparatus where the pressure had been reduced to about 10⁻⁴ Pa, vacuumbaking at 170° C. for 30 minutes was performed in a heating chamber ofthe vacuum evaporation apparatus, and then the substrate was cooled downfor about 30 minutes.

Next, the substrate was fixed to a holder provided in the vacuumevaporation apparatus so that a surface of the substrate provided withthe anode 1101 was faced downward.

After reducing the pressure of the vacuum evaporation apparatus to 10⁻⁴Pa, 4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP) and molybdenum(VI)oxide were deposited by co-evaporation so that the weight ratio of CBPto molybdenum oxide was 2:1, whereby the hole-injection layer 1107 wasformed. The thickness of the hole-injection layer 1107 was 60 nm.

Next,9-(3-{dispiro[9H-fluorene-9,9′(10′H)-anthracene-10′,9″-(9H)fluorene]2′-yl}phenyl)-9H-carbazole(abbreviation: 2mCzPDfha) that is the anthracene compound represented byStructural Formula (103) was deposited to a thickness of 20 nm byevaporation, whereby the hole-transport layer 1103 was formed.

On the hole-transport layer 1103, 2mCzPDfha (abbreviation) that is theanthracene compound represented by Structural Formula (103) andtris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(Mptz1-mp)₃]) were deposited to a thickness of 30 nmby evaporation so that the weight ratio of 2mCzPDfha to [Ir(Mptz1-mp)₃]was 1:0.06, and then2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole(abbreviation: mDBTBIm-II) and Ir(Mptz1-mp)₃ (abbreviation) weredeposited thereon to a thickness of 10 nm by evaporation so that theweight ratio of mDBTBIm-II to Ir(Mptz1-mp)₃ was 1:0.06, whereby thelight-emitting layer 1104 was formed.

bathophenanthroline (abbreviation: BPhen) was deposited to a thicknessof 15 nm by evaporation, whereby the electron-transport layer 1105 wasformed.

Furthermore, lithium fluoride was deposited to a thickness of 1 nm onthe electron-transport layer 1105 by evaporation, whereby anelectron-injection layer 1108 was formed. Lastly, a 200-nm-thickaluminum film was formed as a cathode 1102 functioning as a cathode.Thus, the light-emitting element was manufactured. Note that in all theabove evaporation steps, evaporation was performed by aresistance-heating method.

The element structure of the manufactured light-emitting element 3 isshown below.

TABLE 5 Hole- Electron- Electron- Functional injection Hole-transporttransport injection layer layer layer Light-emitting layer layer layerLight- Thickness 60 nm 20 nm 30 nm 10 nm 15 nm 1 nm emitting StructureCBP:MoOx = 2mCzPDfha 2mCzPDfha:[Ir(Mptz1- mDBTBIm-II:[Ir(Mptz1- BPhenLiF element 3 2:1 mp)₃] = mp)₃] = 1:0.06 1:0.06 Anode: 110 nm ITSOCathode: 200 nm Al<<Operation Characteristics of Light-Emitting Element>>

The light-emitting element 3 thus obtained was sealed in a glove boxunder a nitrogen atmosphere without being exposed to the air. Then, theoperation characteristics of the light-emitting element 3 were measured.Note that the measurement was carried out at room temperature (in anatmosphere kept at 25° C.).

FIG. 22 shows current density-luminance characteristics of thelight-emitting element 3. In FIG. 22, the vertical axis representsluminance (cd/m²) and the horizontal axis represents current density(mA/cm²). FIG. 23 shows voltage-luminance characteristics of thelight-emitting element 3. In FIG. 23, the vertical axis representsluminance (cd/m²) and the horizontal axis represents voltage (V). FIG.24 shows luminance-current efficiency characteristics of thelight-emitting element 3. In FIG. 24, the vertical axis representscurrent efficiency (cd/A) and the horizontal axis represents luminance(cd/m²). FIG. 25 shows voltage-current characteristics of thelight-emitting element 3. In FIG. 25, the vertical axis representscurrent (mA) and the horizontal axis represents voltage (V). FIG. 26shows chromaticity characteristics of the light-emitting element 3. InFIG. 26, the vertical axis represents chromaticity and the horizontalaxis represents luminance.

FIG. 22 demonstrates that the use of 2mCzPDfha (abbreviation) that isone embodiment of the present invention for a hole-transport layer and alight-emitting layer enables a highly efficient element to be obtained.According to FIG. 26, the light-emitting element 2 has a small change inchromaticity that depends on luminance and has excellent carrierbalance. In addition, excellent chromaticity can be obtained and2mCzPDfha (abbreviation) that is one embodiment of the present inventionis suitable as a host material for an element emitting phosphorescencein the blue region because 2mCzPDfha (abbreviation) has a high T₁ level.Table 6 shows initial values of main characteristics of thelight-emitting element 3 at a luminance of approximately 1000 cd/m².

TABLE 6 Current Current Power Voltage Current density ChromaticityLuminance efficiency efficiency (V) (mA) (mA/cm²) (x, y) (cd/m²) (cd/A)(lm/W) Light- 6.6 0.10 2.5 (0.19, 0.31) 660 26 13 emitting element 3

The above results demonstrate that the light-emitting element 3manufactured in this example is a blue light-emitting element with highefficiency.

FIG. 27 shows an emission spectrum of the light-emitting element 3,which was obtained by applying a current of 0.1 mA to the light-emittingelement 3. In FIG. 27, the vertical axis represents emission intensity(arbitrary unit) and the horizontal axis represents wavelength (nm). Theemission intensity is shown as a value relative to the greatest emissionintensity assumed to be 1. As shown in FIG. 27, the emission spectrum ofthe light-emitting element 3 has the maximum emission wavelength ataround 472 nm. This means that the light-emitting element 3 emits bluelight.

Example 7

In this example, the HOMO levels, LUMO levels, T₁ levels, andglass-transition temperatures (Tg) of the anthracene compounds 2mTPDfha(abbreviation) (Structural Formula (100)) and 2mCzPDfha (abbreviation)(Structural Formula (103)), each of which is one embodiment of thepresent invention represented by General Formula (G1) in Embodiment 1,were measured. The HOMO level, LUMO level, T₁ level, andglass-transition temperature (Tg) of 2tBuDfha (abbreviation) were alsomeasured as a comparative example. Table 7 shows measurement results.Note that shown below is the structural formula of 2tBuDfha(abbreviation).

The HOMO levels of thin films of 2mCzPDfha (abbreviation) and 2mTPDfha(abbreviation) were measured with AC-2 and AC-3 (each produced by RikenKeiki, Co., Ltd.), respectively. The LUMO levels of 2mCzPDfha(abbreviation) and 2mTPDfha (abbreviation) were each obtained asfollows: an energy gap (Bg, ΔE) was obtained from an absorption spectrumof the thin film, and the LUMO level was obtained by the measured HOMOlevel and the obtained energy gap.

The T₁ levels of 2mCzPDfha (abbreviation) and 2mTPDfha (abbreviation)were each obtained as follows: the thin film was cooled down to 10 K andthen irradiated with excitation light to obtain an emission spectrum,which was time-resolved to find a phosphorescent peak, and the value ofthe peak on the shortest wavelength side of the phosphorescent wasconverted into an energy value.

The glass-transition temperatures of 2mCzPDfha (abbreviation) and2mTPDfha (abbreviation) were each measured with a differential scanningcalorimeter (Pyris 1 DSC, produced by PerkinElmer, Inc.).

TABLE 7 Solution Thin film (CV) [eV] (AC-2 or AC-3) [eV] Compound HOMOLUMO HOMO LUMO ΔE T₁ level [nm] Tg [° C.] (100) 2mTPDfha ND −2.20 −6.06−2.17 3.89 453 169 (103) 2mCzPDfha −5.90 −2.16 −5.91 −2.41 3.50 — 1852tBuDfha ND ND −6.58 −2.69 3.89 — 151

It was found that the anthracene compounds of the present invention havedeep HOMO levels. It was also found that the anthracene compounds haverelatively shallow LUMO levels because of their wide Bg.

It was also found that the anthracene compounds each have a high T₁level and can be used as a host material for a material emitting lightin the visible range. The anthracene compounds can be suitably used foran element emitting phosphorescence with a short wavelength,particularly phosphorescence in the blue or green region. In particular,2mTPDfha (abbreviation) has Bg as wide as that of 2tBuDfha(abbreviation) and has a particularly high S₁ level.

Table 7 also shows oxidation potentials (HOMO) and reduction potentials(LUMO) of solutions of 2mTPDfha (abbreviation) and 2mCzPDfha(abbreviation), which were obtained in the CV measurement described inExample 1 and Example 2. Clear peaks were not detected when scan wasperformed to 1.5 V on the oxidation side and to −3 V on the reductionside. This is probably because a Dfha skeleton is difficult to oxidizeand reduce. This indicates that when an aryl group is bonded to the2-position of an anthracene skeleton as in the anthracene compound ofthe present invention, the Dfha skeleton is easily oxidized or reduced.Thus, 2mTPDfha (abbreviation) and 2mCzPDfha (abbreviation) probably havehigher carrier-transport properties and drive voltages of an elementthan 2tBuDfha (abbreviation) and Dfha.

It was also found that the anthracene compounds of the present inventioneach have high Tg and thus have excellent heat resistance. This isprobably because the Dfha (9,10-di(fluoren-9,9′-diyl)-9,10-anthracene)skeleton itself has high Tg. It was also found that the anthracenecompounds of the present invention in each of which the aryl group isbonded to the Dfha skeleton have Tg much higher than that of 2tBuDfha(abbreviation) in which only an alkyl group is bonded. Thus, it isthought that when the anthracene compounds of the present invention areused for an element, the element can have excellent heat resistance.

The above indicates that the anthracene compounds of the presentinvention can be suitably used for a light-emitting element because oftheir deep HOMO levels, shallow LUMO levels, high T₁ levels, andexcellent heat resistance. The anthracene compounds of the presentinvention are each thought to be suitable as a host material for anelement emitting phosphorescence with a short wavelength, particularlyphosphorescence in the blue or green region.

A material with a high T₁ level generally has a problem in that the heatresistance (Tg) is low because of a small molecular weight. It can besaid that, in contrast, the anthracene compounds of the presentinvention each have excellent heat resistance as well as a high T₁level.

Example 8

In this example, the HOMO levels, LUMO levels, and T₁ levels of 2mTPDfha(abbreviation) (Structural Formula (100)) and 2mCzPDfha (abbreviation)(Structural Formula (103)), each of which is the anthracene compound ofone embodiment of the present invention represented by General Formula(G1) in Embodiment 1, were calculated. The HOMO levels, LUMO levels, andT₁ levels of 2tBuDfha (abbreviation), 2CzPDfha (abbreviation), and Dfha(abbreviation) were also calculated as comparative examples. Shown beloware the structural formulae of the compounds.

The calculating method is described below. Note that Gaussian 09 wasused as the quantum chemistry computational program. A high performancecomputer (Altix 4700, manufactured by SGI Japan, Ltd.) was used for thecalculations.

First, the most stable structure in the singlet state was calculatedusing the density functional theory. As a basis function, 6-311 (a basisfunction of a triple-split valence basis set using three contractionfunctions for each valence orbital) was applied to all the atoms. By theabove basis function, for example, 1s to 3s orbitals are considered inthe case of hydrogen atoms, while 1s to 4s and 2p to 4p orbitals areconsidered in the case of carbon atoms. Furthermore, to improvecalculation accuracy, the p function and the d function as polarizationbasis sets were added respectively to hydrogen atoms and atoms otherthan hydrogen atoms. As a functional, B3LYP was used. In addition, theLUMO level and HOMO level of the structure were each calculated.

Next, the most stable structure in the triplet state was calculated. Theenergy of the T₁ level was calculated from an energy difference betweenthe most stable structures in the singlet state and in the tripletstate. As a basis function, 6-311G (d, p) was used. As a functional,B3LYP was used.

The calculation results are shown in Table 8.

TABLE 8 Compound HOMO [eV] LUMO [eV] ΔE [eV] T₁ level [nm] (100)2mTPDfha −5.93 −1.17 4.76 442 (103) 2mCzPDfha −5.53 −1.23 4.30 4432tBuDfha −5.92 −1.13 4.79 441 2CzPDfha −5.51 −1.22 4.28 461 Dfha −5.96−1.14 4.82 441

The above results indicate that the Dfha(9,10-di(fluoren-9,9′-diyl)-9,10-anthracene) skeleton itself has anextremely high T₁ level. The above results also indicate that 2mTPDfha(abbreviation) and 2mCzPDfha (abbreviation), each of which is theanthracene compound of one embodiment of the present invention and ineach of which a substituent is bonded to the 2-position of theanthracene skeleton, also have extremely high T₁ levels. The aboveresults also indicate that 2mCzPDfha (abbreviation), in which acarbazol-9-yl group is bonded via m-phenylene to the substituent bondedto the 2-position of the anthracene skeleton, has a higher T₁ level than2CzPDfha (abbreviation), in which a carbazol-9-yl group is bonded viap-phenylene to the substituent. Thus, 2mCzPDfha (abbreviation) is moresuitable than 2CzPDfha (abbreviation) as a host material for an elementemitting phosphorescence with a shorter wavelength.

This is probably because of a difference in spin density distribution.FIGS. 28A and 28B show spin density distributions of 2mCzPDfha(abbreviation) and 2CzPDfha (abbreviation), respectively, which werecalculated by the above-described method.

In 2mCzPDfha (abbreviation), as shown in FIG. 28A, the spin density isdistributed from fluorene bonded to the 9-position of anthracene to thevicinity of a nitrogen atom of carbazole bonded to phenylene through abenzene skeleton on the 2-position side to the 4-position side of theanthracene and phenylene bonded to the 2-position of the anthracene.

The spin density is distributed to the entire part of carbazole in2CzPDfha (abbreviation) as shown in FIG. 28B in contrast to 2mCzPDfha(abbreviation), in which the spin density is distributed to the nitrogenatom of carbazole. Thus, 2mCzPDfha (abbreviation) is more unstable interms of energy and has a higher T₁ level than 2CzPDfha (abbreviation).

Thus, 2mTPDfha (abbreviation) and 2mCzPDfha (abbreviation), in each ofwhich the substituent is bonded to the 2-position of the anthraceneskeleton at the meta-position of the benzene ring in the substituent,have T₁ levels as high as those of 2tBuDfha (abbreviation) and Dfha(abbreviation).

A comparative light-emitting element 1, a comparative light-emittingelement 2, and a comparative light-emitting element 3, in each of which2tBuDfha (abbreviation) was used for a light-emitting layer, aredescribed below with reference to FIG. 7. Shown below are molecularstructures of organic compounds used in the comparative light-emittingelement 1.

<<Manufacture of Comparative Light-Emitting Element 1>>

First, a glass substrate over which a film of indium tin oxidecontaining silicon (ITSO) with a thickness of 110 nm had been formed asthe anode 1101 was prepared. A surface of the ITSO was covered with apolyimide film so that an area of 2 mm×2 mm of the surface was exposed.As pretreatment for forming the light-emitting element over thesubstrate, the surface of the substrate was washed with water and bakedat 200° C. for 1 hour, and then UV ozone treatment was performed for 370seconds. Then, the substrate was transferred into a vacuum evaporationapparatus where the pressure had been reduced to about 10⁻⁴ Pa, vacuumbaking at 170° C. for 30 minutes was performed in a heating chamber ofthe vacuum evaporation apparatus, and then the substrate was cooled downfor about 30 minutes.

Next, the substrate was fixed to a holder provided in the vacuumevaporation apparatus so that a surface of the substrate provided withthe anode 1101 was faced downward.

After reducing the pressure of the vacuum evaporation apparatus to 10⁻⁴Pa, 4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP) and molybdenum(VI)oxide were deposited by co-evaporation so that the weight ratio of CBPto molybdenum oxide was 2:1, whereby the hole-injection layer 1107 wasformed. The thickness of the hole-injection layer 1107 was 60 nm. Notethat the co-evaporation is an evaporation method in which a plurality ofdifferent substances are concurrently vaporized from the respectiveevaporation sources.

Next, a film of 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP) wasformed to a thickness of 20 nm by evaporation, whereby thehole-transport layer 1103 was formed.

Then, on the hole-transport layer 1103, 2tBuDfha that was the anthracenecompound used as the comparative example andtris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III)(abbreviation: Ir(Mptz1-mp)₃) were deposited to a thickness of 30 nm byevaporation so that the weight ratio of 2tBuDfha to Ir(Mptz1-mp)₃ was1:0.06, and then2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole(abbreviation: mDBTBIm-II) andtris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(Mptz1-mp)₃]) were deposited thereon to a thickness of10 nm by evaporation so that the weight ratio of mDBTBIm-II to[Ir(Mptz1-mp)₃] was 1:0.06, whereby the light-emitting layer 1104 wasformed.

Next, bathophenanthroline (abbreviation: BPhen) was deposited to athickness of 15 nm by evaporation, whereby the electron-transport layer1105 was formed.

Furthermore, lithium fluoride was deposited thereon to a thickness of 1nm on the electron-transport layer 1105 by evaporation, whereby anelectron-injection layer 1108 was formed. Lastly, a 200-nm-thickaluminum film was formed as the cathode 1102. Thus, the light-emittingelement was manufactured. Note that in all the above evaporation steps,evaporation was performed by a resistance-heating method.

The element structure of the manufactured comparative light-emittingelement 1 is shown below.

TABLE 9 Hole- Hole- Electron- Electron- Functional injection transporttransport injection layer layer layer Light-emitting layer layer layerComparative Thickness 60 nm 20 nm 30 nm 10 nm 15 nm 1 nm light-emittingStructure CBP:MoOx = mCP 2tBuDfha:[Ir(Mptz1- mDBTBIm-II:[Ir(Mptz1- BPhenLiF element 1 2:1 mp)₃] = mp)₃] = 1:0.06 1:0.06 Anode: 110 nm ITSOCathode: 200 nm Al<<Manufacture of Comparative Light-Emitting Element 2>>

Components other than the light-emitting layer 1104 were manufactured inthe same manner as the comparative light-emitting element 1. Thelight-emitting layer 1104 was formed as follows: on the hole-transportlayer 1103, 2tBuDfha (abbreviation) that was the anthracene compoundused as the comparative example,3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy),andtris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(Mptz1-mp)₃]) were deposited to a thickness of 30 nmby evaporation so that the weight ratio of 2tBuDfha to 35DCzPPy and[Ir(Mptz1-mp)₃] was 1:0.3:0.06, and then2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole(abbreviation: mDBTBIm-II) andtris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(Mptz1-mp)₃]) were deposited thereon to a thickness of10 nm by evaporation so that the weight ratio of mDBTBIm-II to[Ir(Mptz1-mp)₃] was 1:0.06.

The element structure of the manufactured comparative light-emittingelement 2 is shown below.

TABLE 10 Hole- Hole- Electron- Electron- Functional injection transporttransport injection layer layer layer Light-emitting layer layer layerComparative Thickness 60 nm 20 nm 30 nm 10 nm 15 nm 1 nm light-Structure CBP:MoOx = mCP 2tBuDfha:35DCzPPy:[Ir(Mptz1-mDBTBIm-II:[Ir(Mptz1- BPhen LiF emitting 2:1 mp)₃] = mp)₃] = element 21:0.3:0.06 1:0.06 Anode: 110 nm ITSO Cathode: 200 nm Al<<Manufacture of Comparative Light-Emitting Element 3>>

The anode 1101 and the hole-injection layer 1107 were formed in the samemanner as the comparative light-emitting element 1.

On the hole-injection layer 1107, 2tBuDfha (abbreviation) that was theanthracene compound used as the comparative example was deposited to athickness of 20 nm by evaporation, whereby the hole-transport layer 1103was formed.

On the hole-transport layer 1103, 2tBuDfha that was the anthracenecompound of the comparative example andtris(2-phenylpyridinato)iridium(III) (abbreviation: [Ir(ppy)₃]) weredeposited to a thickness of 40 nm by evaporation so that the weightratio of 2tBuDfha to [Ir(ppy)₃] was 1:0.06, whereby the light-emittinglayer 1104 was formed.

Next, 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole(abbreviation: mDBTBIm-II) was deposited to a thickness of 15 nm byevaporation, and then bathophenanthroline (abbreviation: BPhen) wasdeposited thereon to a thickness of 20 nm by evaporation, whereby theelectron-transport layer 1105 was formed.

Furthermore, lithium fluoride was deposited to a thickness of 1 nm onthe electron-transport layer 1105 by evaporation, whereby theelectron-injection layer 1108 was formed. Lastly, a 200-nm-thickaluminum film was formed as the cathode 1102. Thus, the light-emittingelement was manufactured. Note that in all the above evaporation steps,evaporation was performed by a resistance-heating method.

The element structure of the manufactured comparative light-emittingelement 3 is shown below.

TABLE 11 Hole- Hole- Electron- Functional injection transportLight-emitting injection layer layer layer layer Electron-transportlayer layer Comparative Thickness 60 nm 20 nm 40 nm 15 nm 20 nm 1 nmlight-emitting Structure CBP:MoOx = 2tBuDfha 2tBuDfha:[Ir(ppy)₃] =mDBTBIm-II BPhen LiF element 3 2:1 1:0.06 Anode: 110 nm ITSO Cathode:200 nm Al<<Operation Characteristics of Light-Emitting Element>>

The comparative light-emitting elements 1, 2, and 3 thus obtained weresealed in a glove box under a nitrogen atmosphere without being exposedto the air. Then, the operation characteristics of the comparativelight-emitting elements 1, 2, and 3 were measured. Note that themeasurement was carried out at room temperature (in an atmosphere keptat 25° C.).

FIG. 29 shows luminance-current efficiency characteristics of thecomparative light-emitting elements 1 and 2. In FIG. 29, the verticalaxis represents current efficiency (cd/A) and the horizontal axisrepresents luminance (cd/m²). FIG. 30 shows voltage-currentcharacteristics of the comparative light-emitting elements 1 and 2. InFIG. 30, the vertical axis represents current (mA) and the horizontalaxis represents voltage (V). FIG. 31 shows chromaticity characteristicsof the comparative light-emitting elements 1 and 2. In FIG. 31, thevertical axis represents chromaticity and the horizontal axis representsluminance.

FIG. 32 shows emission spectra of the comparative light-emittingelements 1 and 2, which were obtained by applying a current of 0.1 mA tothe comparative light-emitting elements 1 and 2. In FIG. 32, thevertical axis represents emission intensity (arbitrary unit) and thehorizontal axis represents wavelength (nm). The emission intensity isshown as a value relative to the greatest emission intensity assumed tobe 1. As shown in FIG. 32, the emission spectra of the comparativelight-emitting elements 1 and 2 each have the maximum emissionwavelength at around 466 nm. This means that the comparativelight-emitting elements 1 and 2 emit blue light.

FIG. 33 shows voltage-current characteristics of the comparativelight-emitting element 3. In FIG. 33, the vertical axis representscurrent (mA) and the horizontal axis represents voltage (V). Inaddition, FIG. 34 shows chromaticity characteristics of the comparativelight-emitting element 3. In FIG. 34, the vertical axis representschromaticity and the horizontal axis represents luminance.

FIG. 35 shows an emission spectrum of the comparative light-emittingelement 3, which was obtained by applying a current of 0.5 mA to thecomparative light-emitting element 3. In FIG. 35, the vertical axisrepresents emission intensity (arbitrary unit) and the horizontal axisrepresents wavelength (nm). The emission intensity is shown as a valuerelative to the greatest emission intensity assumed to be 1. As shown inFIG. 35, the emission spectrum of the comparative light-emitting element3 has the maximum emission wavelength at around 510 nm. This means thatthe comparative light-emitting element 3 emits green light.

Table 12 shows initial values of main characteristics of the comparativelight-emitting elements 1, 2, and 3 at a luminance of approximately 1000cd/m².

TABLE 12 Current Current Power Voltage Current density ChromaticityLuminance efficiency efficiency (V) (mA) (mA/cm²) (x, y) (cd/m²) (cd/A)(lm/W) Comparative 7.2 0.24 6.0 (0.17, 0.28) 1280 21 9.3 light-emittingelement 1 Comparative 6.0 0.09 2.2 (0.17, 0.26) 630 29 15 light-emittingelement 2 Comparative 14 2.23 56 (0.30, 0.62) 1140 2.0 0.5light-emitting element 3

FIG. 29 demonstrates that the comparative light-emitting elements 1 and2 are each a light-emitting element that emits blue phosphorescence andhas high efficiency. This is probably because the T₁ level of 2tBuDfha(abbreviation) is high as calculated in Example 7. In addition, FIG. 31demonstrates that the comparative light-emitting elements 1 and 2 eachhave a small change in chromaticity that depends on luminance and haveexcellent carrier balance.

The comparative light-emitting element 2 has lower drive voltage andhigher efficiency than the comparative light-emitting element 1. This isprobably because 2tBuDfha (abbreviation) has the deep HOMO level and theshallow LUMO level as shown in the measurement results in Example 7 andis relatively difficult to oxidize and reduce. Thus, as shown in FIG.30, the drive voltage is reduced by mixing 2tBuDfha (abbreviation) and35DCzPPy (abbreviation) that was a carrier-transport material in thelight-emitting layer. In addition, the comparative light-emittingelement 2 had higher efficiency than the comparative light-emittingelement 1 because of the excellent carrier balance. The anthracenecompounds of the present invention each also have a relatively deep HOMOlevel and a relatively shallow LUMO level; thus, by mixing any of theanthracene compounds of the present invention and a carrier-transportmaterial such as PCCP (abbreviation) or 35DCzPPy (abbreviation) thedrive voltage is reduced and the efficiency is improved.

FIG. 36 shows voltage-current characteristics of the comparativelight-emitting element 3 and the light-emitting element 2 described inExample 5. In each of the elements, the same compound is used as a hostof the hole-transport layer and a host of the light-emitting layer(2tBuDfha (abbreviation) was used in the comparative light-emittingelement 3, and 2mCzPDfha (abbreviation) was used in the light-emittingelement 2). Current flows in the light-emitting element 2 more easilythan in the comparative light-emitting element 3 when voltage isincreased (i.e., the line representing the light-emitting element 2 issteeper than that representing the comparative light-emitting element 3in FIG. 36). One of the factors is probably that the light-emittingelement 2, in which 2mCzPDfha (abbreviation) is used for thehole-transport layer, has a higher hole-transport property than thecomparative light-emitting element 3, in which 2tBuDfha (abbreviation)is used for the hole-transport layer. In other words, acarrier-transport property is thought to be improved when an aryl groupis bonded to the 2-position of an anthracene skeleton.

The above results show that the anthracene compounds of the presentinvention each have a high T₁ level, a high Tg, and a carrier-transportproperty, and thus are each suitable as a host material or acarrier-transport material for a light-emitting element, particularly anelement emitting phosphorescence in the blue and green regions.

This application is based on Japanese Patent Application serial no.2013-069849 filed with Japan Patent Office on Mar. 28, 2013, the entirecontents of which are hereby incorporated by reference.

What is claimed is:
 1. A light-emitting element comprising: an anode; a cathode; a hole-transport layer: a light-emitting layer; and an electron-transport layer, wherein the hole-transport layer, the light-emitting layer, and the electron-transport layer are provided between the anode and the cathode, wherein the light-emitting layer comprises an anthracene compound represented by General Formula (G1) and a phosphorescent compound,

wherein α represents an unsubstituted m-phenylene group or a substituted or unsubstituted 3,3′-biphenyldiyl group, wherein Ar represents any of a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted carbazolyl group, a substituted or unsubstituted dibenzothiophenyl group, a substituted or unsubstituted dibenzofuranyl group, a substituted or unsubstituted triphenylenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted phenanthrenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted pyridyl group, a substituted or unsubstituted pyrimidyl group, a substituted or unsubstituted dibenzoquinoxalinyl group, a substituted or unsubstituted benzimidazolyl group, and a substituted or unsubstituted benzoxazolyl group, and wherein in the case where a substituent is bonded to Ar, the substituent is a phenyl group, a biphenyl group, or an alkyl group having 1 to 6 carbon atoms.
 2. The light-emitting element according to claim 1, wherein the hole-transport layer comprises a hole-transport organic compound, and wherein the electron-transport layer comprises an electron-transport organic compound.
 3. The light-emitting element according to claim 1, wherein the light-emitting layer comprises an electron-transport organic compound or a hole-transport organic compound.
 4. The light-emitting element according to claim 1, wherein a phosphorescence wavelength peak is less than or equal to 570 nm.
 5. An electronic device comprising: an operation key; and the light-emitting element according to claim
 1. 6. A light-emitting element comprising: an anode; a cathode; a hole-transport layer: a light-emitting layer; and an electron-transport layer, wherein the hole-transport layer, the light-emitting layer, and the electron-transport layer are provided between the anode and the cathode, wherein the light-emitting layer comprises a compound represented by Structural Formula (100) and a phosphorescent compound


7. A light-emitting element comprising: an anode; a cathode; a hole-transport layer: a light-emitting layer; and an electron-transport layer, wherein the hole-transport layer, the light-emitting layer, and the electron-transport layer are provided between the anode and the cathode, wherein the light-emitting layer comprises a compound represented by Structural Formula (103) and a phosphorescent compound


8. A light-emitting element comprising: an anode; a cathode; a hole-transport layer: a light-emitting layer; and an electron-transport layer, wherein the hole-transport layer, the light-emitting layer, and the electron-transport layer are provided between the anode and the cathode, wherein the light-emitting layer comprises a compound represented by Structural Formula (112) and a phosphorescent compound 